JP5072794B2 - Optical scanning device - Google Patents

Description

  The present invention relates to an optical scanning device used in an image forming apparatus such as a digital copying machine or a laser beam printer, and more particularly to an optical scanning device provided with a reflecting member in the middle of an imaging lens.

  In a conventional optical scanning apparatus, a light beam modulated and emitted in accordance with an image signal from a light source unit that generates a light beam is periodically deflected and scanned using a deflection unit such as a rotating polygon mirror (polygon mirror). Next, the light beam deflected by the polygon mirror is imaged in a spot shape on a photosensitive recording medium, for example, a photosensitive drum, which is a surface to be scanned, by an fθ lens system having fθ characteristics to form a latent image. .

  For example, as shown in FIG. 7, the laser light emitted from the light source 1 becomes parallel light by the collimator lens 2, passes through the cylindrical lens 3, and is shaped to a predetermined size by the aperture 4. This light beam is deflected and scanned by a rotating polygon mirror 5 and imaged on a photosensitive drum as a surface to be scanned by an fθ lens system 6 (6a, 6b) as an imaging lens to form a light spot. The light spot is linearly scanned perpendicular to the rotation direction of the photosensitive drum 100 to form a latent image.

  In such an optical scanning device, about 300 mm is required from the deflection point to the imaging point in some cases. Therefore, the projection area of the optical scanning device requires a large area. In recent years, in order to make the optical scanning device compact, a folding mirror 7a is provided between the imaging lenses 6a and 6b, and the optical path is folded to make the optical scanning device compact.

  On the other hand, the arrangement of the imaging lenses 6a and 6b as described above requires a high positional accuracy of 0.1 mm or less in a three-dimensional manner. There has been a problem that image quality is remarkably deteriorated due to misalignment or bending of scanning lines. Further, the optical system lens is often composed of a plurality of two or more lenses in order to contain optical aberrations. For the above reason, when the folding mirror 7a is provided between the imaging lenses 6a and 6b, imaging is performed. The relative position between the lenses 6a and 6b and the folding mirror 7a is also required to have high accuracy.

  From such background of downsizing the optical scanning device and ensuring the positional accuracy of the imaging optical system, for example, the method described in Patent Document 1 is provided with a folding mirror between the imaging lenses. A method of arranging the second lens so as to overlap the lens is described.

For example, Patent Document 2 proposes that a reflecting member (orthogonal mirror) is provided between the front lens group and the rear lens group, and is fixed integrally by a fixing member having means for regulating the relative positions thereof. .
JP 2001-33723 A JP-A-5-88102

  However, according to the method described in Patent Document 1, there is a problem that the positional accuracy of the first lens and the second lens depends on the position of the positioning member provided between the two lenses.

  Further, the method described in Patent Document 2 also has a problem that the positional accuracy of both lenses and the folding mirror depends on the result of the fixing member integrated. Furthermore, there is no description on how to assure the position of the integrated unit in the optical box. According to this structure, since one member is interposed rather than attaching both lenses and a folding mirror directly to an optical box, it has a structure with one error factor.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an optical scanning device that can reduce the size of the optical scanning device and can more accurately ensure the correlation position of the optical box, the reflecting member, and the imaging optical means.

The above object is achieved by an optical scanning device according to the present invention. In summary, the present invention comprises a light source that generates a light beam;
Deflection means for deflecting and scanning the generated light beam;
Imaging optical means for imaging the deflected and scanned light beam as a spot on the surface to be scanned;
In an optical scanning device having
The imaging optical means includes a first lens that passes the deflected and scanned light beam, a reflecting member that reflects the light beam that has passed through the first lens, and a second lens that passes the reflected light beam; Consists of
In the optical scanning device, the first lens and the second lens are disposed so as to abut against the reflecting member.

  According to the present invention, the optical scanning device regulates the position by bringing the imaging lens (first and second lenses) into contact with the reflecting surface of the reflecting member (folding mirror). Therefore, unlike the conventional example, the relative positional accuracy between the two is not affected by the production of separate parts, and the reliability is higher.

  Hereinafter, the optical scanning device according to the present invention will be described in more detail with reference to the drawings.

Example 1
1 and 2 show a schematic cross section of an embodiment of an optical scanning apparatus 100 according to the present invention. In this embodiment, the optical scanning device 100 includes an imaging lens (imaging optical means) in which a polygon mirror (deflecting means) 5 and two imaging lenses (first and second lenses 8A and 8B) are integrally formed. 8. A folding mirror (reflection member) 9 is provided.

  Although not shown in FIGS. 1 and 2, the optical scanning device 100 of this embodiment also has an optical system for directing a light beam to the polygon mirror 5, as shown in FIG. A light source 1, a collimator lens 2, a cylindrical lens 3, and an aperture 4 are provided.

  Therefore, according to the optical scanning device 100 of the present embodiment, for example, as shown in FIG. 7, the laser light emitted from the light source 1 becomes parallel light by the collimator lens 2, passes through the cylindrical lens 3, and is predetermined by the aperture 4. Shaped to size.

  As shown in FIG. 2, this light beam is deflected and scanned by the rotating polygon mirror 5, and then the light beam passes through one refracting surface 8a of the imaging lens 8, and then passes through the refracting surface 8b. . This light beam is reflected by the reflecting surface 9a of the folding mirror 9, passes again through the refracting surface 8b of the imaging lens 8, and subsequently passes through the refracting surface 8c, and finally onto the drum surface which is the scanned surface. It is imaged as a spot.

  As described above, by providing three or more refracting surfaces (8a, 8b, 8c) in one lens, not only the optical scanning device 100 can be made compact, but also the relative shape between the refracting surfaces can be reduced. There is a merit that the positional accuracy is improved.

  However, for example, when the refractive surfaces 8a and 8c are given power in the sub-scanning direction, the following can be considered as a disadvantage of being integrally formed. That is, compared with a lens configuration in which the refractive surfaces 8a and 8c are independent and the position can be adjusted, the relative position of the folding mirror with respect to the reflecting surface 9a is required to have very high accuracy.

  Therefore, in the present invention, image quality is improved by arranging the imaging lens 8 and the folding mirror 9 that require high relative positional accuracy in contact with each other.

  FIG. 3 is a perspective view of the imaging lens 8.

  As shown in FIG. 3, the rib 10 and the rib 11 are provided at both ends of the imaging lens 8, and the abutting portions 10a, 10b and 11a are provided. The three abutting portions 10a, 10b and 11a are folded back. By attaching them to the reflecting surface 9a, the relative position between them can be assured with high accuracy.

  As described above, there is a feature of the present invention in that members that require positional accuracy are arranged in contact with each other without using another member. However, this is made possible by reflecting the reflecting surface 9a of the folding mirror 9. Is due to the fact that it is a single surface and is not an orthogonal mirror.

  Therefore, according to the configuration of the present embodiment, the optical axis OA that passes through the lower first lens 8A and enters the reflecting surface 9a and the optical axis OB that is reflected and passes through the upper second lens 8B are: They are not parallel to each other. That is, the light that passes through the imaging lens 8 and enters the reflecting surface 9a and the light that is reflected and passes through the imaging lens 8 again have a distance as the distance from the reflecting surface 9a increases. For this reason, the imaging lens 8 in which the first and second lenses 8A and 8B are integrally molded is necessarily arranged close to the reflecting surface 9a, so that the lens can be reduced in size.

  FIG. 1 is a cross-sectional view showing a configuration of an optical scanning device 100 according to an embodiment of the present invention. A polygon mirror 5, an imaging lens 8, and a folding mirror 9 are disposed in an optical box 13 of the optical scanning device. As described above, in the imaging lens 8, the abutting portions 10a and 10b of the ribs 10 and 11 provided on the end surface and the abutting portion 11a (not shown) are brought into contact with the reflecting surface 9a of the folding mirror 9. Position guarantee is made.

  4, 5 and 6 are perspective views showing the configuration of the present embodiment.

  As described above, the imaging lens 8 is brought into contact with the reflecting surface 9a of the folding mirror 9, and the back surface thereof is urged by the pressing portions 14a and 15a of the leaf springs 14 and 15. The leaf springs 14 and 15 are fixed by using the reaction force and hooking holes 14b and 15b to protrusions 16 and 17 provided in the optical box 13. Further, regarding the regulation in the height direction of the imaging lens 8, the lower surface of the imaging lens 8 is brought into contact with the projections 18 and 19 provided on the optical box 13, and the upper surface is pressed against the pressing portion 14c of the leaf springs 14 and 15. , 15c to achieve. Further, the position restriction of the imaging lens 8 in the beam scanning direction is realized by fitting the boss 12 provided at the lower center of the imaging lens 8 into the oblong hole 20 provided in the optical box 13. .

  On the other hand, regarding the position regulation of the folding mirror 9, the reflecting surface 9 a is brought into contact with three points of the abutting portions 20, 21, 22 provided on the optical box 13, and a leaf spring 23 attached to the optical box 13, It implement | achieves by energizing with the 24 pressing parts 23a and 24a. Further, the lower surface of the folding mirror 9 is brought into contact with the projections 25 and 26 provided on the optical box 13, and the upper surface is urged by the pressing portions 23b and 24b of the leaf springs 23 and 24 to maintain the posture. .

  However, in this configuration, naturally, the force of the pressing portions 23a and 24a of the plate springs 23 and 24 that urge the folding mirror 9 is applied to the pressing portions 14a of the plate springs 14 and 15 that urge the imaging lens 8. It is assumed that it is stronger than 15a.

  As described above, with such a configuration, the position of the reflecting surface 9 a of the folding mirror 9 is guaranteed with respect to the optical box 13. As a result, the position of the imaging lens 8 having a highly correlated positional relationship with the folding mirror 9 with respect to the optical box can be ensured with high accuracy, and the optical scanner can be made compact and the image quality can be improved.

  Also, when assembling the optical scanning device, if such a simple butting configuration is used, high relative position accuracy can be maintained and work efficiency can be improved without time-consuming position adjustment as in the prior art. To do.

  In the present embodiment, the imaging lens 8 has been described as a lens having three refracting surfaces, but may be a plurality of independent imaging lenses having two refracting surfaces as in the past.

  As described above, the optical scanning device 100 according to the present invention controls the position by bringing the imaging lens 8 into contact with the reflecting surface 9a of the folding mirror 9. Therefore, unlike the conventional example, the relative positional accuracy of both is not influenced by the production of separate parts, and the reliability is higher.

  In addition, since the position is regulated by bringing the reflecting surface 9a of the folding mirror 9 into contact with the optical box 13, the relative positional accuracy between the optical box 13 and the folding mirror 9 is also high. In general, high correlation position accuracy is maintained in the optical box 13, the folding mirror 9, and the imaging lens 8, and the quality of scanning exposure can be improved as compared with the conventional configuration.

  In addition, since a plurality of imaging lenses (first and second lenses 8A and 8B) are arranged vertically, a reduction in size is achieved.

1 is a schematic cross-sectional view showing an internal configuration in an embodiment of an optical scanning device according to the present invention. It is a part of optical path diagram of the optical scanning device shown in FIG. It is a perspective view of the imaging lens shown in FIG. FIG. 2 is a perspective view of an imaging lens, a folding mirror, and a leaf spring of the optical scanning device shown in FIG. 1. FIG. 2 is a perspective view of an imaging lens, a folding mirror, and a leaf spring of the optical scanning device shown in FIG. 1. It is a perspective view of the optical box of the optical scanning device shown in FIG. It is a perspective view which shows an example of the conventional optical scanning device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source 2 Collimator lens 3 Cylindrical lens 4 Aperture 5 Rotating polygon mirror (deflection means)
6 Imaging lens (imaging optical means)
7 Folding mirror (reflective member)
8 Imaging lens (imaging optical means)
8A 1st lens 8B 2nd lens 9 Folding mirror (reflection member)
10, 11 Ribs 10a, 10b, 11a Abutting portion 13 Optical box

Claims (4)

A light source that generates a light beam;
Deflection means for deflecting and scanning the generated light beam;
Imaging optical means for imaging the deflected and scanned light beam as a spot on the surface to be scanned;
In an optical scanning device having
The imaging optical means includes a first lens that passes the deflected and scanned light beam, a reflecting member that reflects the light beam that has passed through the first lens, and a second lens that passes the reflected light beam; Consists of
The optical scanning device according to claim 1, wherein the first lens and the second lens are disposed so as to abut against the reflecting member.   The optical scanning device according to claim 1, wherein the reflecting surface of the reflecting member is disposed to abut against the optical box.   The optical scanning device according to claim 1, wherein the first lens and the second lens are integrally formed. The reflective surface of the reflective member is one surface,
4. The light according to claim 1, wherein an optical axis that passes through the first lens and enters the reflecting surface is not parallel to an optical axis that is reflected and passes through the second lens. Scanning device.

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