JP3194242B2 - Laser scanning optical system - Google Patents

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 system applied to a copying machine, a facsimile machine, a printer and the like.

FIG. 3 is a perspective view showing a schematic configuration of a laser scanning optical system.

1 is a semiconductor laser, 2 is a collimating lens, 3 is a cylinder lens, 4 is a polygon mirror rotated by a polygon motor (not shown), 5 is an Fθ lens, 6 is a valet toroidal lens, and 7 is a printer or the like. The photosensitive drum is arranged in the image forming apparatus and rotates in the sub-scanning direction y.

[0004] Laser light emitted from the semiconductor laser 1 (indicated by a dashed line in the figure) is incident on a collimating lens 2, is converted into parallel light, passes through a cylinder lens 3, and is a polygon mirror which is a rotating polygon mirror. 4 is incident. The laser light is deflected in the main scanning direction x by the polygon mirror 4 rotating at a high speed and enters the Fθ lens 5.

The Fθ lens 5 corrects the image forming position so that the laser beam scans the main scanning line x on the photosensitive drum 7 at a constant speed, and narrows down the laser beam to a beam diameter corresponding to the pixel density. The laser beam emitted from the Fθ lens 5 passes through the valet toroidal lens 6 to form an electrostatic latent image on the photosensitive drum 7.

[0006] FIG. 4 is an explanatory view of the correction to the laser light by the barrel toroidal lens shown in FIG.

The polygon mirror 4 has a central axis directly connected to the polygon motor, and deflects the reflected light of the laser light incident on the mirror surface 4a by twice the rotation angle by rotating at a constant rotation speed. At this time, when the mirror 4a is tilted due to the inclination of the central axis of the polygon mirror 4, the laser beam is shifted on the photosensitive drum 7 from the main scanning line L in the sub-scanning direction y corresponding to the tilt amount. Would. Therefore, in the laser scanning optical system, the cylinder lens 3 and the valet toroidal lens 6 having lens power only in the sub-scanning direction y are arranged before and after the polygon mirror 4 to correct the inclination of the mirror surface 4a.

The laser beam reflected by the polygon mirror 4 is imaged on a photosensitive drum 7 by an Fθ lens 5 and a valet toroidal lens 6. At this time, if the Fθ lens 5 and the valet toroidal lens 6 are considered as one combination lens, the mirror surface 4a
The upper image is an object point, the image on the photosensitive drum 7 is an image point, and the Fθ lens 5 and the valet toroidal lens 6
Becomes a conjugate relationship. Therefore, all the light emitted from the object point always converges on the image point, and the position of the laser beam on the photosensitive drum 7 does not change even if the mirror surface 4a is inclined.

FIG. 5 is a perspective view showing a main part of a conventional laser scanning optical system.

Reference numeral 11 denotes a mounting portion formed on an optical base (not shown) constituted by a case, a frame, and the like. Reference numeral 12 denotes a holder for supporting the valet toroidal lens 6, and reference numeral 13 denotes a mounting portion 11.
Is a leaf spring that holds the holder 12 at a fixed position.

The two leaf springs 13 are brought into close contact with the vicinity of one end thereof and the vicinity of the end of the holder 12, respectively, to form screw holes 12a, 13a.
The screw 14 is screwed into the screw holes 12b and 13b. Further, the leaf spring 13 is screwed by screws 14 screwed around the other end screw hole 11 b in close contact to the mounting surface 11a of the mounting portion 11, the 13c. At this time, the holder 12
Is configured to elastically contact the positioning surface 11c and the positioning surface 11d formed on the mounting portion 11 by the elastic force of the leaf spring 13, and is positioned in the optical axis direction z by elastically contacting the positioning surface 11c. Also, by elastically contacting the positioning surface 11d, positioning is performed in the sub-scanning direction y. Further, as shown in the front view of FIG. 6 , the holder 12 has a positioning protrusion 12c projecting from a contact surface with the positioning surface 11c, and the positioning protrusion 12c is provided between a pair of positioning protrusions 11e formed on the mounting portion 11. Are positioned in the main scanning direction x.

By causing the holder 12 to resiliently contact the mounting portion 11 by the elastic force of the leaf spring 13, the valet toroidal lens 6 moves the mounting portion 11 and the holder 12 in the main scanning direction x, the sub-scanning direction y, and the optical axis direction z. Held in a fixed position defined by Here, since the holder 12 is in elastic contact with the mounting portion 11 by the elastic force of the leaf spring 13, even if the thermal expansion coefficients of the mounting portion 11 and the holder 12 are different, there is a thermal effect between the mounting portion 11 and the mounting portion 11. No distortion occurs. Therefore, even when the laser scanning optical system is used in an environment having a large temperature change, the valet toroidal lens 6 is prevented from being displaced by the influence of distortion, and is reliably held at a fixed position in three directions.

[0013]

However, in the above-described laser scanning optical system, the mounting portion 11 and the holder 12 must be machined with high precision in order to position the valet toroidal lens 6 with high precision. In addition, since the shape of the leaf spring 13 is complicated, the cost of the apparatus increases.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a laser scanning optical system in which a valet toroidal lens is fixed with a simple structure, and the valet toroidal lens is prevented from being displaced by an influence of a temperature change.

[0015]

In order to solve the above-mentioned problems, the present invention provides a rotary polygon mirror for reflecting laser light and deflecting it in the main scanning direction, and a sub-scan of the laser light deflected by the rotary polygon mirror. barrel and barrel toroidal lens for correcting the deviation in the direction, and an optical base in which the barrel toroidal lens is fixed, the barrels toroidal lens formed of plastic, and the mounting portion of the barrel toroidal lens in at least said optical base Ray formed of plastic with the same coefficient of thermal expansion as toroidal lens
In the scanning optical system, fitted with a valet toroidal lens
Part, and the fitting part is fitted into the
Forming a positioning groove to position the retoroidal lens
And press-fit into the positioning groove when fitting the fitting part.
And an elastic member for fixing the fitting portion .

[0016]

[0017]

Further, the laser beam is reflected and reflected in the main scanning direction.
The rotating polygon mirror that deflects the light,
Barretroy that corrects the shift of the light in the sub-scanning direction
The dull lens and the valet toroidal lens are fixed.
Optical base and a valet toroidal lens
Formed of styx and at least on the optical base
The ballet toroidal lens mounting part
It is made of plastic with the same thermal expansion coefficient as the dull lens.
In the laser scanning optical system, a fitting portion is formed in the valet toroidal lens, and a positioning groove for positioning the valet toroidal lens by fitting the fitting portion to the mounting portion is formed. At the time of fitting, a fixing pin which is inserted into the insertion hole communicating with the positioning groove and the insertion hole formed in the fitting portion to fix the fitting portion is provided.

[0019]

According to the above means, even if the valet toroidal lens and the mounting portion are made of plastics having the same coefficient of thermal expansion and the mounting portion, the valet toroidal lens is closely attached to the mounting portion and fixed. No distortion due to thermal effects occurs.

[0020]

Further, the elastic member is fixed by frictional force in the positioning groove by the fitting portion formed in the valet toroidal lens, the positioning groove formed in the mounting portion, and the elastic member pressed into the positioning groove. Fix the fitting part.

Further, a fitting portion formed in the ballet toroidal lens, a positioning groove formed in the mounting portion, an insertion hole communicating with the positioning groove, and a fixing pin inserted into the insertion hole formed in the fitting portion. The fixing pin fixes the fitting portion in the positioning groove.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. In FIGS. 1 and 2, 3 and 4
The members corresponding to the members described based on are denoted by the same reference numerals, and description thereof will be omitted.

[0024]

[0025]

[0026]

[0027]

[0028]

[0029]

FIG. 1 is a perspective view showing an example of a main part of an embodiment of a laser scanning optical system according to the present invention .

Reference numeral 31 denotes a mounting portion formed on the optical base (not shown) and formed of the same plastics as the valet toroidal lens 16, and 32 denotes an elastic member formed in a cylindrical shape.

The mounting portion 31 has a substantially U-shaped cross section orthogonal to the optical axis direction z, and has a positioning hole 31a formed substantially at the center in the main scanning direction x. The positioning groove 31b extends in the sub-scanning direction y.

The ballet toroidal lens 16 has a fitting portion 16b and a fitting portion 16c from one side face 16a and both end faces.
Is protruding.

When the valet toroidal lens 16 is fixed, the fitting portion 16c is inserted into the positioning groove 31b so that the fitting portion 16c is inserted.
b fits into the positioning hole 31a, and the side surface 16a comes into contact with the mounting portion 31. Further, the elastic member 32 is inserted into the positioning groove 31b, and is brought into contact with the fitting portion 16c in the positioning groove 31b.
Here, since the elastic member 32 has a diameter longer than the opening width of the positioning groove 31b, the elastic member 32 elastically contacts the inner surface of the positioning groove 31b and is fixed in the sub-scanning direction y by a frictional force. The valet toroidal lens 16 is positioned in the main scanning direction x and the optical axis direction z by fitting the fitting portions 16b and 16c into the positioning holes 31a and the positioning grooves 31b, and the side surface 16a is attached to the mounting portion 31. Is positioned in the sub-scanning direction y.
Further, the elastic member 32 is press-fitted into the positioning groove 31b to fit the fitting portion 16c.
By this, the valet toroidal lens 16 positioned in three directions is fixed.

Ballet toroidal lens 16 and mounting portion 31
Are made of the same plastic and have the same coefficient of thermal expansion. As a result, even if the two members are brought into close contact with each other, it is possible to prevent the occurrence of distortion in the barrel-toroidal lens 16 or the mounting portion 31 due to the thermal influence. The displacement of the toroidal lens 16 can be prevented. Furthermore, the ballet toroidal lens is provided by the elastic member 32.
By fixing 16, the structure for fixing and the fixing operation can be simplified.

FIG. 2 is a perspective view showing another example of the main part in this embodiment.

Reference numeral 41 denotes a mounting portion formed on the optical base (not shown) and formed of the same plastics as the valet toroidal lens 16, reference numeral 42 denotes a cylindrical split pin, and reference numeral 43 denotes a caulking pin.

The mounting portion 41 has a positioning hole 41a formed substantially at the center in the main scanning direction x, and positioning grooves 41b extend at both ends. Further, insertion holes 41c penetrating in the optical axis direction z and communicating with the positioning grooves 41b are formed at both ends of the mounting portion 41, respectively.

The ballet toroidal lens 16 has a fitting portion 16b and a fitting portion 16c from one side surface 16a and both end surfaces.
Are formed, and an insertion hole 16d penetrating in the optical axis direction z is formed in the fitting portion 16c.

When the valet toroidal lens 16 is fixed, the fitting portion 16c is inserted into the positioning groove 41b so that the fitting portion 16c is inserted.
b fits into the positioning hole 41a, and the side surface 16a comes into contact with the mounting portion 41. At this time, the insertion hole 41c and the insertion hole 16d are configured so as to communicate at the same position. A split pin 42 is inserted from below into the communicating insertion holes 41c and 16d, and a swage pin 43 is inserted into this split pin 42 from above. The inner diameter of the split pin 42 is formed to be smaller than the diameter of the pin of the swage pin 43, and by inserting the swage pin 43 into the split pin 42, the split pin 42 expands in the radial direction to insert the insertion holes 41c and 16d. To prevent the split pin 42 and the caulking pin 43 from falling off,
The fitting portion 16c is fixed in the positioning groove 41b.

Ballet toroidal lens 16 and mounting portion 41
Are made of the same plastic and have the same coefficient of thermal expansion. As a result, even when the two members are brought into close contact with each other, it is possible to prevent the occurrence of distortion in the barrel-toroidal lens 16 or the mounting portion 41 due to thermal influence. The displacement of the toroidal lens 16 can be prevented. Further, by fixing the valet toroidal lens 16 with the split pin 42 and the caulking pin 43, the structure for fixing and the fixing operation can be simplified.

[0042]

As described above, according to the present invention,
Even if the valet toroidal lens and the mounting portion are made of plastics having the same coefficient of thermal expansion and the valet toroidal lens is closely attached to the mounting portion and fixed, the valet toroidal lens and the mounting portion do not undergo distortion due to thermal influence. The displacement of the valet toroidal lens fixed to the mounting portion can be prevented. Furthermore, Valerto
The fitting part of the Roydal lens, the positioning groove of the mounting part,
Elastic member friction in the positioning groove
The barrel is fixed by force and fixing the fitting part.
Fixing toroidal lens and balleroidal lens
The structure for fixing the lens can be simplified.

[0043]

[0044]

Further, by means of the fitting portion of the valet toroidal lens, the positioning groove of the mounting portion, the insertion hole of the fitting portion and the fixing pin inserted into the insertion hole communicating with the positioning groove,
With the fixing pin that the fixing pin fits into the first insertion hole,
By fixing the fitting portion in the positioning groove by the fixing pin, the operation for fixing the valet toroidal lens and the configuration for fixing the valerto toroidal lens can be simplified.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of a main part of an embodiment of a laser scanning optical system according to the present invention.

FIG. 2 is a perspective view showing another example of a main part in the embodiment.
is there.

FIG. 3 is a perspective view showing a schematic configuration of a laser scanning optical system.
is there.

FIG. 4 is a view showing the lens formed by the valet toroidal lens shown in FIG . 3;
FIG. 4 is an explanatory diagram of correction for user light .

FIG. 5 is a perspective view showing a main part of a conventional laser scanning optical system.
FIG.

FIG. 6 is a front view of the holder shown in FIG . 5;

[Explanation of symbols]

16… Barrel toroidal lens, 16c… Mating part, 16d…
Insertion holes, 31 , 41: mounting part , 31b, 41b: positioning groove,
32 ... elastic member, 41c ... insertion hole, 42 ... split pin, 4
3… Crimping pin

Claims (2)

(57) [Claims] A rotating polygon mirror that reflects laser light and deflects the laser light in the main scanning direction, a valet toroidal lens that corrects a deviation of the laser light deflected by the rotating polygonal mirror in a sub-scanning direction, and the valet toroidal lens. and an optical base to be fixed, over the barrels toroidal lens formed of plastic, and to form a mounting portion of the barrel toroidal lens in at least the optical base with equal plastics barrel toroidal lens and the thermal expansion coefficient In the scanning optical system , a fitting portion is formed on the valet toroidal lens, and
The fitting part is fitted to the attachment part, and a ballet toroidal lens is formed.
Forming positioning groove for positioning, and fitting of fitting part
Occasionally, an elastic member is pressed into the positioning groove to fix the fitting portion.
A laser scanning optical system comprising an elastic member . 2. The laser beam is reflected and deflected in the main scanning direction.
Rotating polygon mirror and the laser beam deflected by the rotating polygon mirror.
Barrel toroidal lens for correcting misalignment in the sub-scanning direction
Lens and the optics to which the valet toroidal lens is fixed
With a base and plastic ballistic toroidal lens
And at least in the optical base
Barrel toroidal lens
Lens made of plastics with the same coefficient of thermal expansion as
In The scanning optical system, to form a fitting portion into barrels toroidal lens, and the preparative
The fitting part is fitted to the attachment part, and a ballet toroidal lens is formed.
Forming positioning groove for positioning, and fitting of fitting part
Sometimes, the insertion hole and the fitting part communicating with the positioning groove
Fixing that is inserted into the formed insertion hole to fix the fitting part
Features and, Relais chromatography The scanning optical system further comprising a pin.