JP3110816B2 - Optical scanning device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning device, and more particularly, to an optical scanning device having a reflecting member provided between image forming lenses.

[0002]

2. Description of the Related Art In a laser printer, digital copier, or the like, an image is obtained by emitting a light beam modulated according to image information from a light source such as a laser diode and deflecting the light beam to scan a surface to be scanned. An optical scanning device for exposing the light is used.

For example, as shown in FIG. 4, modulated light emitted from a light source 1 composed of a laser diode is converted into a parallel beam by a collimator lens 2 and shaped into a predetermined size by an aperture 3. The parallel light beam is deflected by a rotating polygon mirror 4 and is imaged on a surface to be scanned, for example, a photosensitive drum 6 by an fθ lens 5 serving as an imaging lens to form a light spot. 6, a latent image is formed by performing a linear scan orthogonal to the rotation direction.

Recently, in order to reduce the size of the main unit, the optical scanning device has been reduced in size by providing mirrors 7 and 8 in the middle of the optical path and bending the optical axis. In addition, in order to reduce the size or improve the scanning accuracy, for example, as shown in JP-A-1-134416 or JP-A-1-164917, a plurality of light beams from a plurality of light sources are reflected by one polygon mirror. There has been a proposal to deflect and arrange the imaging lenses of the respective light beams in an overlapping manner.

[0005]

The elements and members constituting these optical scanning devices are positioned and fixed on a housing or a substrate. In particular, generally, an fθ lens composed of a concave lens 5a and a convex lens 5b is generally used. The arrangement of No. 5 requires high precision, and even if a processing error or distortion occurs even slightly, there is a problem that the image quality is remarkably deteriorated due to irregularity of a light spot, deviation of an image formation position, or bending of a scanning line.

Further, the optical scanning device is required to be further downsized. However, if the number of mirrors 7 and 8 is further increased to increase the number of reflections, the optical scanning device becomes thicker and the adjustment becomes complicated. Occurs. The proposal shown in the above publication also
Even if some miniaturization can be achieved, there are problems such as a complicated device and an increase in the thickness of the polygon mirror. If a mechanism for finely adjusting the relative position of the fθ lens is provided to solve these problems, the process becomes complicated, and disadvantages in cost, reliability, and durability.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has as its object to reduce the size of an optical scanning device, to facilitate assembly, reduce cost, and improve reliability.

[0008]

In order to achieve the above object, the present invention deflects and scans a light beam emitted from a light source by a rotary deflector and scans the deflected and scanned light beam by an imaging lens. In an optical scanning device that forms an image on a surface, an imaging lens is formed of a front group and a rear group of lenses each formed in a strip shape ,
On the opposite side of the rotary deflector, a reflection member for reflecting a light beam is provided, and a lens of the front group and a lens of the rear group are respectively provided.
A reference member is arranged so as to be superposed in a direction perpendicular to the deflection scanning surface of the light beam by the rotary deflector, and a reflecting member is provided.
By integrating two reflecting surfaces whose perpendiculars are orthogonal to each other.
It consists of orthogonal mirrors. And, the rotation bias
The light beam deflected by the director is scanned by the
And reflected by the reflecting member,
Light beam passes through the rear lens group on the surface to be scanned.
Is formed .

[0009] and of the front group and rear group of the imaging lens lens
May be provided with a fixing member for fixing together with the above-described reflecting member regulates the relative position.

[0010]

In the optical scanning device having the above-described structure, the front lens group and the rear lens group that constitute the imaging lens are separated from each other.
Deflection scanning of light beam by rotating deflector with matching quasi-planes
And superimposed in the direction perpendicular to the surface
Reflector provided on the opposite side of the group of lenses from the rotary deflector
Material, two reflective surfaces whose perpendiculars are perpendicular to each other are integrated
Since it is configured by an orthogonal mirrors and comprising, Ru can be summarized in its entirety comparator <br/> transfected. In particular, since the lens of the front lens group and the rear group formed in a strip shape has been superimposed perpendicularly to the deflection scanning plane of the light beam are disposed, front lens group and the rear group
The parallelism between the optical axis and the generatrix of the lens is maintained, and eccentricity is suppressed.

Further , the reflecting member is constituted by an orthogonal mirror.
Therefore, even if it is assembled in an inclined manner, the optical axis for reciprocation of the light beam is kept parallel, and both optical axes have a certain interval in the direction in which the front and rear lens groups are superimposed. On the other hand, the light beam does not enter obliquely.

[0012] The imaging lens and the reflecting member which is compactly as mentioned above, be fixed together to regulate the relative position by the fixing member, the relative positions easy to assemble is kept accurately trust The performance is improved . Moreover, one
Since it can be handled as an imaging block , total assembly and maintenance are simplified.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a sectional view showing a configuration of an optical scanning device according to an embodiment of the present invention.

The optical scanning device 10 comprises a light source (not shown), a collimator lens, an aperture, etc., a rotary deflector 13 comprising a polygon mirror 11, and a flat motor 12 for rotating the polygon mirror 11, and an imaging lens 14. The concave lens 15 and the convex lens 16, which are the lenses of the front and rear groups formed in a strip shape, and the orthogonal mirror 17, which is a reflecting member including two reflecting surfaces 17a and 17b whose perpendiculars are orthogonal to each other, It is composed of

The light source section (not shown) of the rotary deflector 13 including a light source, a collimator lens, an aperture, and the like are the same as or similar to those described in the conventional example of FIG. The concave lens 15, the convex lens 16 and the orthogonal mirror 17 are respectively fixed to upper and lower support plates 21 and
2, the integrated imaging block 20 is fixedly mounted on a substrate 23 of the optical scanning device 10 together with other members and elements. The upper part of the substrate 23 has a cover 24
Covered by

A parallel light beam emitted from a light source unit (not shown) is incident on the polygon mirror 11 from the back, and is rotated and deflects and scans on a plane perpendicular to the paper surface to move the lower concave lens 15 from left to right in the figure. To the orthogonal mirror 17
The light is reflected by the reflecting surfaces 17a and 17b, and passes through the upper convex lens 16 from right to left in the opposite direction parallel to the time of incidence. The convergent light beam transmitted through the convex lens 16 is reflected by the mirror 1
The light is reflected at 8 and faces a photosensitive drum (not shown) equivalent to the conventional example, and forms an image on that surface.

[0017] The quadrature mirror 17, the light from the beam travels an optical path shifted by parallel constant distance from each other in opposite directions, as the concave lens 15 and convex lens 16 are contradictory transmitting direction of the light beam on the optical axis The reference surfaces 15a and 16a are combined so as to coincide with each other.

When a lens is processed into a strip shape, one of its edge surfaces, generally, one of the edge surfaces which becomes its longer side is used as a reference surface, and the reference surface is the optical axis of the lens and the generatrix. The center of the light beam that has been deflected and scanned is parallel and precisely finished with respect to a line that cuts through the lens. Therefore, if the reference surfaces of the concave lens 15 and the convex lens 16 are overlapped so as to be coincident with each other, the optical axis and the generatrix are held in parallel with high precision, and no adjustment for that is necessary.

The orthogonal mirror (also referred to as a “roof mirror”) 17 can maintain the parallelism of the reflected light if the 90 ° is accurately finished at the time of processing. Even if it rotates about an axis perpendicular to and tilts up and down during mounting, the parallelism is not lost. If this orthogonal mirror 17 is integrally formed of plastic, for example, and aluminum is deposited on the reflection surface, after the first inspection is completed, a large number of high-precision mirrors can be obtained inexpensively and assembled with confidence. I can do it.

FIG. 2 is an exploded perspective view showing an example of the configuration of the imaging block 20 assembled (sub-assembled) as described above. On the upper surface of the lower support plate 22, the concave lens 15
The protrusions a, b, and c for regulating the position of the orthogonal mirror 17, the protrusions d and e for regulating the position of the orthogonal mirror 17, and the columns f and g having two female screw holes are integrally formed.

The left and right positions of the concave lens 15 are defined by the projections a and b, and the front and rear positions and inclinations are defined by the projections a and b and the projections c.
e, the front and rear position and inclination are convex protrusions d and e.
Are fitted in the grooves 17d and 17e (not shown) of the orthogonal mirror 17, respectively.

On the lower surface (not shown) of the upper support plate 21, three protrusions, which slightly differ in size from the protrusions a, b, and c of the lower support plate 22, but define the position of the convex lens 16, and protrusions d and
Two projections are provided to regulate the position of the orthogonal mirror 17 as in e. The reference surface 15a is provided on the upper surface of the lower support plate 22.
The concave lens 15 and the orthogonal mirror 17 are positioned at the correct positions, and the convex lens 16 with the reference surface facing downward is superposed on the upper surface of the concave lens 15 to form the imaging lens 14.

If the upper support plate 21 is placed at the correct position, the position of the convex lens 16 is also correctly set. Therefore, the screws 26a, 2b are passed through the holes 21a, 21b of the upper support plate 21.
If the upper and lower support plates 21 and 22 are screwed together by screwing the 6b into the columns g and f of the lower support plate 21, the members constituting the image forming block 20 are integrally fixed at the correct positions, and may go out of order. Absent.

FIG. 3 shows a concave lens 1 fixed in this way.
FIG. 3 is a perspective view showing a state of an imaging lens 14 including a convex lens 5 and a convex lens 16. The concave lens 15 and the convex lens 16, which are meniscus lenses respectively arranged above and below, have the transmission directions of the light beam to be deflected and scanned opposite to each other. In this embodiment, the concave lens 15 has a concave front, and the convex lens 16 has a convex front.

As described above, the concave lens 15 and the convex lens 16 have been described as being independent from each other, as in the conventional example. However, according to the present invention, optically between the front lens group and the rear lens group. Although a reflecting member is provided, the lenses of the front group and the rear group are superposed mechanically, so that the concave lens 15 and the convex lens 16 can be integrally formed by, for example, plastic. When the imaging lens 14 is integrally formed in this way, not only the number of components is reduced and the cost is reduced, but also the relative position is not at all likely to be out of order, so that the reliability is improved.

The front lens group and the rear lens group each have one lens.
Although the description has been made of the case where the lens comprises a plurality of lenses, one or both of them may be constituted by a plurality of lenses. Furthermore, if the relative position between the imaging lens 14 and the orthogonal mirror 17 can be adjusted, the dimensional error of each lens can be corrected by itself. This is compared to adjusting the distance between the front group lens and the rear group lens as before,
It is much easier because no optical axis shift or tilt occurs.

As described above, the optical scanning device according to the present invention is not limited to the dimension in the direction along the optical path of the light beam.
And the dimension in the direction perpendicular to it is minimized,
It can be made compact and easy to assemble to reduce costs and improve reliability. And before
The parallelism of the optical axis and generatrix of the group lens and the rear group lens
Maintained and eccentricity is suppressed. In addition, folding
The optical axis of the returned light beam is kept parallel.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of an optical scanning device according to an embodiment of the present invention.

FIG. 2 is an exploded perspective view showing a part of the configuration of the imaging block shown in FIG. 1;

3 is a perspective view showing an example of the shape of an imaging lens in the imaging block shown in FIG.

FIG. 4 is a perspective view showing a conventional example of an optical scanning device.

[Explanation of symbols]

Reference Signs List 10 optical scanning device 13 rotary deflector 14 imaging lens 15 concave lens (lens in front group) 16 convex lens (lens in rear group) 17 orthogonal mirror (reflective member) 21 upper support plate (fixed member) 22 lower support plate (fixed member) A), b, c, d, e protrusions (means for regulating the position)

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02B 26/10 G02B 7/198

Claims (2)

(57) [Claims] 1. An optical scanning device which deflects and scans a light beam emitted from a light source by a rotary deflector and forms an image of the deflected and scanned light beam on a surface to be scanned by an imaging lens. each was composed of lenses and rear group front group formed in a strip shape, the lens of the front group and rear group
A reflection member for reflecting a light beam is provided on the opposite side to the rotary deflector, and the front lens group and the rear lens group are arranged so that their respective reference planes are one.
Itasa was superposed in a direction perpendicular to the deflection scanning plane of the light beam by the rotating deflector disposed, the reflection member, the reflection of two whose normals are perpendicular to each other
The light beam deflected and scanned by the rotary deflector is constituted by an orthogonal mirror having integrated surfaces.
Transmitted through the front lens group and reflected by the reflecting member,
The reflected light beam passes through the rear lens group
An optical scanning device, wherein an image is formed on the surface to be scanned . 2. A light scanning device according to claim 1, before
A lens of a front group and a rear group of the imaging lens and the reflecting member;
A fixing member that regulates the relative position of the
An optical scanning device, characterized in that digit.