JP2002040348A - Optical unit of laser beam scanning - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable to use the unit being commonly for models having a different relative position of a photosensitive drum, and to improve the possibility of recycle. SOLUTION: An adjustment mechanism 20 for the position of a mirror is provided, in which a turning back mirror 12 is moved in the direction of an optical axis shown by the arrow C and fixed at an arbitrary position, and the turning back mirror 12 is turned around an axis of shaft parts 22 and 26, and adjusted and fixed at an arbitrary angle. The turning back mirror 12 together with a mirror bracket 29 is correctly positioned at one of three predetermined positions in the direction of the optical axis when one of three positioning holes 35a is selected and a positioning pin is inserted into the selected hole. Further, the angle of the turning back mirror 12 is varied by selecting one of three positioning holes 27b on a fixing member 27 and inserting the positioning pin into the selected hole.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser scanning optical unit for scanning a laser beam, and more particularly to a laser scanning optical unit suitable for use in an image forming apparatus such as a digital copying machine, a laser printer, and a facsimile machine.

[0002]

2. Description of the Related Art Conventionally, laser printers and the like use a laser scanning optical unit which deflects a laser beam emitted from a light source by a rotary polygon mirror and scans the laser beam on a photosensitive drum via an optical system. ing. Such a laser scanning optical unit generally includes a light source in an optical housing, a rotary polygon mirror and a drive motor for rotating the rotary polygon mirror,
A scanning lens and the like are housed and covered, and the scanning light is applied to the photosensitive drum through dustproof glass attached to a window formed on a side wall or the like of the optical housing.

In such a laser scanning optical unit,
Even if the components incorporated in the optical housing are the same and the specifications as the laser scanning optical unit are almost the same,
For example, in a model in which the positional relationship between the laser scanning optical unit and the photosensitive drum is different, the same optical housing could not be used in a normal case, so a dedicated optical housing had to be prepared for each model. .
As a result, the time required for the design is increased, and the number of steps for manufacturing dedicated parts is increased, which may significantly increase the cost.

In a conventional laser scanning optical unit, for example, a folding mirror provided at the end of an optical path and reflecting laser light is usually positioned on a mounting surface formed on an optical housing, and is positioned by a leaf spring or the like. It is fixed. In addition, the positional deviation of the scanning line on the photosensitive drum in the sub-scanning direction at the time of assembly is generally regulated by the accuracy of the shape of the optical housing, or by finely adjusting the position and angle of the folding mirror. Or amending it.

However, since the conventional mechanism for adjusting the position and angle of the return mirror is to finely adjust the position and angle of the return mirror, the position and angle of the return mirror are largely changed. By doing so, it was not possible to support different models.

In such a laser scanning optical unit, a synchronization detecting means is generally provided, and the detection of the scanning light by the synchronization detecting means is usually performed on the scanning start side of the photosensitive drum to be scanned. Out of the effective writing range. That is, as shown in FIG.
In the case of a laser scanning optical unit of the type which scans the scanning direction in the direction of arrow A, the reflection mirror 59 for synchronization detection, the cylindrical lens 50 and the synchronization detection sensor 51 constituting the synchronization detection means are provided by a polygon mirror 56 and Imaging lens 58
Are arranged on the scanning start side, which is the lower side in FIG.

Further, as shown in FIG. 9, in the case of a laser scanning optical unit of the type in which the scanning direction of the laser light L is scanned in the direction indicated by the arrow B, the reflection for synchronization detection constituting the synchronization detection means is provided. A mirror 59, a cylindrical lens 50, and a synchronization detection sensor 51 are connected to a polygon mirror 56 and an imaging lens 58.
Are arranged on the scanning start side, which is the upper side in FIG. For this reason, in the case of this laser scanning optical unit, as described above, even if an attempt is made to use the laser scanning unit in a different scanning direction of the scanning light, it cannot be performed.

Therefore, a laser scanning optical unit (deflection scanning device) used in a conventional laser printer or the like is described in, for example, JP-A-10-96873. This laser scanning optical unit includes a light source, a rotating polygon mirror, a drive motor for rotating the rotating polygon mirror, a scanning lens, and the like. After being mounted on the optical housing, the upper opening is closed by a lid, and the scanning light is taken out from the window formed on the side wall of the optical housing toward the rotating drum.

In this optical housing, four support members are formed, and each of the support members has a downward reference surface used for attachment to the main body frame, and an upward reference surface on the opposite surface. Each surface is formed. Therefore, in the case of a model in which the rotating polygon mirror is rotated in a counterclockwise direction as viewed from the plane side and scans the rotating drum in one direction with the scanning light, the downward reference surface of each support member is set to the optical housing. Abut on the support of the body frame,
The optical housing is assembled to the body frame.

[0010] Further, due to design restrictions of the entire apparatus to which the laser scanning optical unit is mounted, the rotary polygon mirror is rotated in the direction opposite to the above-described direction, and the rotating drum is scanned with scanning light in the opposite direction. For models that must be used,
The optical housing is turned upside down so that the upward reference surface of each support member comes into contact with the support portion of the main body frame, and the optical housing is assembled to the main body frame with the bottom wall facing upward.

[0011]

However, in such a laser scanning optical unit in which each supporting member of the optical housing is provided with a downward reference surface and an upward reference surface for attachment to the main body frame, the rotating drum is used. Although the same laser scanning optical unit can be used even when the scanning directions of the above scanning light are different, the following inconvenience may occur.

That is, when scanning with the scanning light in the reverse direction, the optical housing had to be mounted on the main body frame with the bottom wall turned upside down, so that the light source and the rotating polygon mirror were required. Also, since the drive motor for rotating the rotating polygon mirror and the scanning lens are all covered with the optical housing, those parts cannot be seen from above, so when a problem occurs with those parts, There is a problem that it is difficult to check and exchange the information.

Further, since there is no mechanism for changing the incident angle of the scanning light on the rotating drum (photosensitive drum), if it is necessary to change the incident angle of the scanning light on the rotating drum depending on the model, a laser scanning optical unit is required. The whole had to be mounted at an angle.

However, in this case, if the tilt angle is large, the drive motor for rotating the rotary polygon mirror also tilts, and the characteristics of the drive motor change, making the drive unsatisfactory. There is a possibility that a load is applied to the bearing that supports the rotating shaft of the motor, and the life of the bearing is shortened. Further, in order to incline the entire laser scanning optical unit, a space for that is necessary, but in general, the space for inclining the laser scanning optical unit is a very limited space. In many cases, the incident angle of the scanning light is extremely limited and extremely small.

On the other hand, the number of types of image forming apparatuses using such a laser scanning optical unit tends to increase due to diversification of user demands, and new models have been successively added with new functions. As a result, the product life cycle is becoming shorter. As a result, when the disposal of the equipment progresses, there is a concern about environmental pollution due to an increase in the waste.
Therefore, even if the life cycle of the device is advanced, if only some of the units and components can be recycled, the amount of discarded components can be reduced.

The present invention has been made in view of the above problems, and can be used in common even if the models have different positional relations with the photosensitive drums. It is an object of the present invention to provide a laser scanning optical unit that can be partially recycled.

[0017]

In order to achieve the above object, the present invention provides a light source for emitting laser light, a deflecting means for deflecting laser light emitted from the light source, and a laser deflected by the deflecting means. In a laser scanning optical unit provided in an optical housing with an imaging lens for forming an image of light on a surface to be scanned and a folding mirror at the end of an optical path for reflecting a laser beam to change the direction, the folding mirror is connected to an optical axis. And / or a mirror position adjustment mechanism which can be fixed at an arbitrary position by rotating the folding mirror around the longitudinal direction of the folding mirror to an arbitrary angle. Is provided.

The mirror position adjusting mechanism may include means for fixing the return mirror at two or more fixed positions in the optical axis direction, and / or at least the mirror in the rotational direction about the longitudinal direction of the mirror. It is preferable to provide means for fixing at two or more predetermined rotational positions.

In a laser scanning optical unit having the same light source, deflecting means, image forming lens, and folding mirror as those described above in an optical housing, the folding mirror is rotated by using the longitudinal direction of the folding mirror as an axis. A mirror position adjusting mechanism that can be fixed at a plurality of angles is provided, and a fixed angle that can be fixed at a plurality of angles of the folding mirror by the mirror position adjusting mechanism is a laser beam incident on and reflected by the folding mirror. An angle that is perpendicular to the optical axis of the laser light incident on the folding mirror, upward and downward, and an angle that is perpendicular to each of the upward and downward directions. The angle should be in the range of

Further, in any one of the above laser scanning optical units, a synchronization detecting means for receiving a part of the scanning light deflected by the deflecting means and outputting a detection signal is provided, and a main scanning direction of the optical housing is provided. It is preferable that a synchronous detecting means mounting portion for mounting the synchronous detecting means is provided on each of both sides, and the synchronous detecting means can be selectively mounted on either of the synchronous detecting means mounting portions on both sides.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view for explaining a mirror position adjusting mechanism for adjusting the position of a return mirror of a laser scanning optical unit according to the present invention, and FIG. 2 is a view showing the entire configuration of the laser scanning optical unit with a housing cover removed. FIG. 3 is an overall configuration diagram viewed from the plane shown
FIG. 2 is a longitudinal sectional view of the laser scanning optical unit.

The laser scanning optical unit shown in FIGS. 2 and 3 includes a light source, for example, a semiconductor laser that emits a laser beam, a collimating lens that converts the laser beam L emitted from the light source into parallel light, and a collimating lens. And an aperture for shaping the laser light.

The laser scanning optical unit also has a cylindrical lens 5 for condensing the laser light shaped by the aperture of the light source unit 1 in the sub-scanning direction, and reflects the laser light L transmitted through the cylindrical lens 5. A polygon mirror 6 which is a deflecting means which is rotationally driven by a polygon mirror motor 7 for deflecting; an image forming lens 8 which forms an image of a laser beam deflected by the polygon mirror 6 on a surface to be scanned; 9, a cylindrical lens 10 for condensing light from the reflection mirror 9 in the sub-scanning direction, a synchronization detection sensor 11, and a photosensitive drum that reflects scanning light from the imaging lens 8 at the end of the optical path. Folding mirror 12 for turning to the side 18 (FIG. 3), dustproof glass 13 (FIG. 3), and optical housing 1 for holding these optical components
4 and so on.

The upper surface of the optical housing 14 is covered with a housing cover 30, as shown in FIG. In general, the imaging lens 8 generally uses a plurality of lenses having a function of fθ correction and a surface tilt correction of a polygon mirror. In this embodiment, a single lens will be described. Then, the light is reflected by the turning mirror 12 and the dustproof glass 13 is reflected.
The laser beam L that has passed through is incident on a predetermined position on the photosensitive drum 18 at a predetermined angle.

The optical housing 14 includes a reflection mirror 9, a cylindrical lens 10, and a synchronization detection sensor 11 functioning as synchronization detection means for receiving a part of the scanning light deflected by the above-described deflection means and outputting a detection signal. , FIG.
As shown by the solid line and the imaginary line, synchronous detecting means mounting portions are provided on both sides of the optical housing 14 in the main scanning direction (vertical direction in the figure), and synchronous detecting means is mounted on one of the synchronous detecting means mounting portions on both sides. The means can be selectively attached.

The arrangement position of the reflection mirror 9, the cylindrical lens 10, and the synchronization detection sensor 11 is changed according to whether the scanning direction of the laser beam of the model to be mounted is indicated by the arrow A or B in FIG. And a position indicated by a virtual line. As described above, the optical housing 14 of the laser scanning optical unit can be used in common even when the scanning direction for scanning the laser light L is different from that shown by arrows A and B in FIG. . If the scanning direction of the laser beam L is different, the polygon mirror 6 is made to correspond accordingly.
It is also necessary to change the direction of rotation.

As shown in FIG. 1, the folding mirror 12 has both ends in the longitudinal direction fixed to a mirror holder front 21 and a mirror holder rear 23, and is formed in a columnar projecting portion of the mirror holder rear 23. The shaft 26, which is integrally fixed to the fixing member rear 25, is rotatably fitted into the hole 23 a through a hole formed in the rear wall surface 29 a of the mirror bracket 29.

A shaft portion 22 is formed on the end surface of the front portion 21 of the mirror holder, and the shaft portion 22 is rotatably inserted into a hole formed on the front wall surface 29b of the mirror bracket 29.
The shaft portion 22 is fitted and fixed in a center hole of a boss portion 28 integrally formed with a fixing member front 27 formed in a fan shape. As a result, both ends of the folding mirror 12 are rotatably supported by the rear wall surface 29a and the front wall surface 29b of the mirror bracket 29 by the shaft portions 26 and 22.

A hole 25a is formed in the rear portion 25 of the fixing member, and a screw 15 formed in the rear wall surface 29a of the mirror bracket 29 with the screw 15 inserted into the hole 25a (FIG. 1).
(Not shown in the figure), the rear portion 25 of the fixing member is fixed to the mirror bracket 29.

An arc-shaped long hole 2 is provided in front of the fixing member 27.
The fixing member front 27 is fixed to the mirror bracket 29 by screwing a screw 16 inserted into the long hole 27 a into a screw hole 29 c formed in the front wall surface 29 b of the mirror bracket 29. Then, the fixing member front 27 is rotated about the shaft portion 22 within a range allowed by the long hole 27a, and the screw 16 is screwed into the screw hole 29 at an arbitrary position.
c, the shaft portion 22 of the mirror holder front 21 fixing the return mirror 12 is fixed to the front of the fixing member 2.
7, the angle of the folding mirror 12 can be changed to an arbitrary angle.

In this laser scanning optical unit, as shown in FIG. 4, the upper side of the optical housing 14 is covered with the housing cover 30 as described above, and the housing cover 30 is located at a position corresponding to the folding mirror 12. An opening 30a is formed. The opening 30a is shown in FIG.
When the folding mirror 12 is fixed at the position shown in FIG. 4 and the laser beam L reflected by the folding mirror 12 is guided downward in FIG. In this case, the dustproof glass 13 is fixed to the lower opening 14a formed on the lower surface of the optical housing 14.

Further, as shown in FIG. 7, by rotating the front portion 27 of the fixing member 180 degrees and fixing it at the position shown in FIG.
When the folding mirror 12 is fixed at the position shown in FIG. 6, the dustproof glass 13 is fixed on the opening 30a instead of the sealing member 31, and the laser beam L reflected by the folding mirror 12 is guided upward in FIG. At this time, the seal member 31 is fixed to the lower opening 14a formed on the lower surface of the optical housing 14, and the lower opening 14a is closed. As described above, the optical housing 14 according to the present embodiment can be commonly used by a model that guides the laser beam L reflected by the folding mirror 12 upward and a model that guides the laser beam L downward.

As described above, the turning mirror 12 is rotatable about the shaft portions 22 and 26. The turning center is the reflection position Pre of the laser light (scanning light) L on the turning mirror 12. To match. Thus, even when the direction of reflecting the laser beam L is changed to the upward direction shown in FIG. 4 and the downward direction shown in FIG. 6, the photosensitive member is not changed without changing the optical path length of the scanning light. Since the sub-scanning position of the scanning line on the drum 18 (FIG. 3) can be adjusted, high accuracy can be obtained as an adjusting mechanism.

The fixed angle of the folding mirror 12 can be changed.
Furthermore, the position of the fixing member front 27 shown in FIG.
What can be done by changing it within the range allowed by 27a
As described above, the change range of the fixed angle is shown in FIGS.
As shown in FIG.
Laser beam L incident on the folding mirror 12
At right angles to the optical axis of the light L, upward and downward, respectively.
Reflected laser light L ₀And the angles above and below
At right angles (laser light L₀Matches)
Turn the mirror 12 on both sides in the direction of rotation of the mirror 12
Laser light L reflected in the range of 45 degrees or less₁, L₂Nana
Angle can be adjusted. Do this
Is the laser light L₁, L₂Is the laser light L₀45 for
If it exceeds the degree, the light transmittance of the dust-proof glass 13 becomes
This is to prevent it from dropping sharply.
You.

Further, the folding mirror 12 can be arbitrarily moved in the direction of the optical axis by moving the mirror bracket 29 in the direction of the optical axis indicated by the arrow C in FIG. . In other words, three fixing surfaces 29d and 29e on both sides of the mirror bracket 29 fixed to the optical housing 14 (FIG. 2) are provided along the optical axis direction indicated by arrow C.
Long holes 32a, 32b, 32c are formed respectively, and the long holes 32a, 32a,
Each of the guide pins 33 and 34 fixed to or detachable from the optical housing 14 is fitted into the optical housing 14 so as to be relatively movable, and a screw 17 is inserted into each central long hole 32b. It is screwed into the formed screw hole.

Therefore, the long hole 32 of the fixing surface 29d is provided.
b, the screws 17, 17 in the long hole 32b of the fixing surface 29e are loosened, and the mirror bracket 29 is moved in the optical axis direction indicated by the arrow C, and the screws 17, 17 are tightened and fixed. The position 12 can be changed in the optical axis direction (the direction indicated by the arrow C) within the range permitted by the long holes 32a to 32c together with the mirror bracket 29.

Further, three (two) mirrors functioning as means for fixing the mirror angle of the folding mirror 12 at a predetermined rotation position in the rotation direction about the longitudinal direction of the folding mirror 12 are provided at the front of the fixing member 27. Or four or more positioning holes 27b). Also, the front fixed surface 29d of the mirror bracket 29
In addition, three (four even four) mirrors function as means for fixing the folding mirror 12 at a fixed position in the optical axis direction indicated by arrow C.
5 may be formed along the optical axis direction, and a hole 14b having substantially the same diameter as the positioning hole 35a is formed on the bottom surface of the optical housing 14 in FIG.
One is formed as shown in FIG.

Therefore, the three positioning holes 35a
Is selected, and the positioning pin 36 is inserted therein, and the positioning pin 36 is inserted into the optical housing 14.
If it is inserted into the hole 14b on the side, the folding mirror 12 can be accurately positioned together with the mirror bracket 29 at any one of the three fixed positions in the optical axis direction.

Therefore, these three positioning holes 35a are
If the laser scanning optical unit is formed at an accurate position for each model, a positioning hole corresponding to the model to be used is selected from three positioning holes 35a, and a positioning pin is formed there. 36 and insert it into hole 14b
By simply inserting the mirror, it is possible to easily position the mirror at an accurate position in the optical axis direction corresponding to the model using the folding mirror 12.

The three positioning holes 35a are also provided in the fixing surface 29e on the rear side of the mirror bracket 29 along the optical axis direction (three or two or more than three). And a hole 1 having a diameter substantially the same as that of the positioning hole 35a on the bottom surface of the optical housing 14 correspondingly.
4b is formed.

As described above, this laser scanning optical unit is provided with the long holes 32a to 32c in the fixed surfaces 29d and 29e on both sides.
A mirror bracket 29 having three positioning holes 35a formed therein, guide pins 33 and 34 provided before and after the mirror bracket 29 is movably guided in the optical axis direction indicated by arrow C, and a mirror bracket 29, respectively. Two screws 1 before and after fixing the
7 and positioning pin 36 to be fitted into positioning hole 35a
And a hole 14b on the optical housing 14 side for fitting the same.
The mirror position adjusting mechanism 20 composed of the above-described method moves the folding mirror 12 in the direction of the optical axis indicated by the arrow C to accurately position the folding mirror 12 together with the mirror bracket 29 at a fixed position determined by the selected positioning hole 35a. Can be.

The mirror position adjusting mechanism 20 has three
It also has two positioning holes 27b, positioning pins 37 (see FIGS. 5 and 7) fitted into the positioning holes 27b, arc-shaped long holes 27a, screws 16, and screw holes 29c into which the screws 16 are screwed. Therefore, the folding mirror 12 can be fixed at an arbitrary angle by rotating the mirror about the shaft portions 22 and 26 around the mirror longitudinal direction indicated by the arrow E in FIG.

Therefore, for each model having a different positional relationship with the photosensitive drum, the direction of the optical axis of the folding mirror 12 and the predetermined fixed position in which the angle at which the laser beam is incident on the folding mirror 12 are determined by the positioning holes 27b. , 3
By setting according to the position of 5a, it is not necessary to adjust the folding mirror 12 with a large-sized jig, and the assembling property and the exchangeability in the market are facilitated.

The laser scanning optical unit is
In the case of the model in which the photosensitive drum is located below the laser scanning optical unit in FIG. 4, the folding mirror 12 may be fixed at the position shown in the figure by the mirror position adjusting mechanism 20 described above. Conversely, when the photosensitive drum is above the laser scanning optical unit, the folding mirror 12 may be rotated and fixed to the position described with reference to FIG. In this case,
As described above, the dustproof glass 13 is fixed to the upper opening 30a, and the lower opening 14a is covered with the seal member 31.

As described above, this laser scanning optical unit can correspond to the scanning direction of the laser beam whichever type is shown by the arrow A or the arrow B shown in FIG. The position of the photosensitive drum 18 may be slightly different from that of the folding mirror 12 shown in FIG. On the other hand, even if it is a model located above (see FIG. 6) or a model located below (see FIG. 3 and FIG. 4), the same one can be used in common. Further, since the same laser scanning optical unit can be used for a plurality of models, the recyclable range of the components constituting the laser scanning optical unit can be expanded.

The mirror position adjusting mechanism 20 in the above-described embodiment can move the folding mirror 12 in the direction of the optical axis, and furthermore, the folding mirror 12
An example of a mechanism that can be rotated about the longitudinal direction of the mirror as an axis to adjust and fix it at an arbitrary angle has been described, but the mirror position adjusting mechanism has a mechanism that only moves the folding mirror 12 in the optical axis direction. However, even if the mechanism is such that the folding mirror 12 can be rotated about the longitudinal direction of the mirror as an axis and adjusted to an arbitrary angle to be fixed, a model in which the positional relationship with the photosensitive drum is different can be used. This is effective in enabling the same laser scanning optical unit to be commonly used.

[0047]

As described above, according to the present invention, the following effects can be obtained. According to the laser scanning optical unit of the first aspect, the folding mirror can be moved in the optical axis direction and fixed at an arbitrary position, and / or can be fixed at an arbitrary angle by rotating about the mirror longitudinal direction as an axis. The same laser scanning optical unit can be commonly used by changing the position and / or angle of the return mirror even in a model having a different positional relationship with the body drum. Therefore, recyclability is improved.

According to the laser scanning optical unit of the second aspect, the mirror position adjusting mechanism includes means for fixing the folding mirror at at least two or more fixed positions in the optical axis direction, and / or moving the folding mirror along the length of the mirror. It is provided with means for fixing at at least two or more predetermined rotational positions in the rotational direction with the direction as an axis, so that the fixed position can be determined in advance for each model having a different positional relationship with the photosensitive drum. This eliminates the need for a large-scale adjustment using a jig, thereby facilitating assembly and exchangeability in the market.

According to the laser scanning optical unit of the third aspect, the mirror position adjusting mechanism causes the folding mirror to cause the laser light incident on the folding mirror to be reflected upward with respect to the optical axis of the laser light incident on the folding mirror. The angle at which the reflected laser beam is fixed to an angle of 45 degrees or less in the rotational direction of the folding mirror is fixed on both sides around the angle at which the right angle is formed downward and the angle at which the right angle is formed at the upper and lower sides. Therefore, not only a model having a different positional relationship with the photosensitive drum, but also a model in which the scanning surface of the photosensitive drum or the like scanned by laser light is located above or below the laser scanning optical unit. , The same laser scanning optical unit can be commonly used.

According to the laser scanning optical unit of the fourth aspect, the synchronization detecting means is provided with the synchronization detecting means mounting portions on both sides of the optical housing in the main scanning direction. Since the synchronization detecting means can be selectively attached to the same type, the same laser scanning optical unit can be commonly used even if the models have different scanning directions of laser light. Therefore, the applicable models of the same laser scanning optical unit or optical housing can be further expanded.

[Brief description of the drawings]

FIG. 1 is a perspective view for explaining a mirror position adjusting mechanism for adjusting a position of a return mirror of a laser scanning optical unit according to the present invention.

FIG. 2 is an overall structural view of the entire laser scanning optical unit viewed from a plane showing a state in which a housing cover is removed.

FIG. 3 is a longitudinal sectional view of the laser scanning optical unit.

FIG. 4 is a schematic diagram showing a state in which the position of a folding mirror provided in the laser scanning optical unit is fixed to a position where the laser light reflected by the mirror faces downward.

5 is a front view showing a position in front of a fixing member of the mirror position adjusting mechanism when the folding mirror is at the position shown in FIG. 4;

FIG. 6 is a schematic diagram showing a state where the position of the folding mirror is fixed to a position where the laser light reflected by the mirror faces upward.

FIG. 7 is a front view showing a position in front of a fixing member of the mirror position adjusting mechanism when the folding mirror is at the position shown in FIG. 6;

FIG. 8 is a schematic plan view showing an example of a laser scanning optical unit that performs detection of scanning light by a conventional synchronous detection unit outside an effective writing range on a scanning start side of a photosensitive drum. .

9 is a schematic diagram similar to FIG. 8, illustrating an example of a laser scanning optical unit in which scanning light is scanned in a direction opposite to that of FIG.

[Explanation of symbols]

 1: light source unit 6: polygon mirror (deflection means) 8: imaging lens 9: reflection mirror 10: cylindrical lens 11: synchronization detection sensor 12: folding mirror 14: optical housing 20: mirror position adjusting mechanism

Claims (4)

[Claims] A light source for emitting laser light; a deflecting means for deflecting the laser light emitted from the light source; an imaging lens for imaging the laser light deflected by the deflecting means on a surface to be scanned; In the laser scanning optical unit provided at the end of the optical housing with a folding mirror that reflects the laser light and changes the direction, the folding mirror can be moved in the optical axis direction and fixed at an arbitrary position. And / or a mirror position adjusting mechanism provided with a mirror position adjusting mechanism capable of rotating the folding mirror around an axis of a longitudinal direction of the folding mirror to adjust the mirror to an arbitrary angle and fixing the mirror. 2. The mirror position adjusting mechanism includes means for fixing the return mirror at two or more fixed positions in the optical axis direction, and / or a rotation direction about the mirror in a longitudinal direction of the mirror. 2. The laser scanning optical unit according to claim 1, further comprising: means for fixing at two or more predetermined rotational positions. 3. A light source for emitting laser light, deflecting means for deflecting the laser light emitted from the light source, an imaging lens for imaging the laser light deflected by the deflecting means on a surface to be scanned, and an optical path. At the end of the laser scanning optical unit provided in the optical housing with a folding mirror that reflects the laser light to change the direction, wherein the folding mirror is rotated around the longitudinal direction of the folding mirror as an arbitrary plurality of mirrors. A mirror position adjusting mechanism that can be fixed at an angle is provided, and a fixed angle that can be fixed at a plurality of angles of the folding mirror by the mirror position adjusting mechanism is set such that laser light incident on and reflected by the folding mirror is reflected on the folding mirror. Angles that are perpendicular to the optical axis of the incident laser light, upward and downward, respectively, and angles that are perpendicular to the upper and lower angles, respectively. Laser scanning unit, characterized in that the said wrapping angle in the range of less than 45 degrees respectively in the direction of rotation of the mirror on both sides around the. 4. The laser scanning optical unit according to claim 1, further comprising: a synchronization detection unit that receives a part of the scanning light deflected by the deflection unit and outputs a detection signal. In addition, a synchronization detection means mounting portion for mounting the synchronization detection means is provided on both sides of the optical housing in the main scanning direction, and the synchronization detection means can be selectively mounted on any of the synchronization detection means mounting portions on both sides. A laser scanning optical unit characterized in that: