JPH0961739A - Image forming unit for optical scanning - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate the assembly of an image forming optical system including an image forming reflecting mirror and an anamorphic lens while making the best use of compactness in an optical scanner using such an image forming optical system. SOLUTION: In the image forming optical system provided with the image forming reflecting mirror 51 having an image forming function, the anamorphic lens 57 and a mirror 60 bending the optical path of a deflected luminous flux between the mirror 51 and the lens 57, and constituted so that the position of a deflection starting point by a light deflector 4 and the position of a surface to be scanned may be in geometic-optical conjugate relation in a vertical scanning corresponding direction; the mirror 51 and the lens 57 are superposed and integrated in the vertical scanning corresponding direction, and the side surface part in the vertical scanning corresponding direction of either of the mirror 51 and the lens 71, which is long in a horizontal scanning corresponding direction, is set as a mount reference surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning image forming unit.

[0002]

2. Description of the Related Art An optical scanning device for writing by optical scanning has been proposed which uses an image forming reflecting mirror having an image forming function.

FIG. 4 schematically shows an example of an optical arrangement in such an optical scanning device. A divergent light beam from the light source LD1 is converted into a parallel light beam or a weak divergent or weak convergent light beam by the coupling lens 2, and the cylinder lens 3 converts the light beam in the sub-scanning corresponding direction (from the light source to the surface to be scanned). A polygon mirror 4 which is an optical deflector and is condensed on the optical path in a direction parallel to the sub-scanning direction).
A long line image is formed in the vicinity of the deflecting / reflecting surface in the main scanning corresponding direction (direction parallel to the main scanning direction on the optical path from the light source to the surface to be scanned) and is deflected by the polygon mirror 4.

The deflected light beam is reflected by the image forming mirror 5,
It is condensed as a light spot on the surface to be scanned through the anamorphic long lens 7. The photoconductor 8 is arranged with a generatrix (shown by a broken line) aligned with the surface to be scanned, and is optically scanned along the generatrix by the light spot.

The image forming reflecting mirror 5 has an image forming function of collecting the deflected light beam on the surface to be scanned in the main scanning corresponding direction. On the other hand, the elongated lens 7 has a function of condensing the deflected light beam on the surface to be scanned in the sub-scanning corresponding direction together with the imaging reflecting mirror 5.

That is, the elongated lens 7 and the image forming reflecting mirror 5 have a function of making the starting position of the deflection by the polygon mirror 4 and the position of the surface to be scanned have a geometrical optical conjugate relationship in the sub-scanning corresponding direction. This function corrects the surface tilt of the polygon mirror 4.

Prior to the optical scanning of the surface to be scanned, the deflected light beam is reflected by the reflecting surface portion 6 of the imaging reflecting mirror 5 and received by the synchronization detecting element 9, and is output from the synchronization detecting element 9. Based on the setting of the starting point of the optical scanning, each optical scanning is synchronized.

The image forming reflecting mirror 5 is required to have a high degree of accuracy in its disposition state because a slight “tilt error” influences the reflected light flux by a double error, and therefore, relative to the long lens 7. Since the accuracy of the physical relationship is strict, it is troublesome to set up an optical system. On the other hand, when the image forming optical system is used, the optical path of the deflected light beam is folded back, so that the optical scanning device can be made compact.

[0009]

SUMMARY OF THE INVENTION In view of the above-mentioned circumstances, the present invention is an optical scanning device that uses an image forming optical system including an image forming reflecting mirror and an anamorphic lens, and utilizes the compactness while combining the optical system. The task is to make it easy to get a job.

[0010]

SUMMARY OF THE INVENTION In an optical scanning image forming unit according to the present invention, a light beam deflected by an optical deflector is condensed as a light spot on a surface to be scanned by an image forming optical system to form a light spot on the surface to be scanned. It is used in an optical scanning device that performs optical scanning.

In the optical scanning device, the "imaging optical system" bends the optical path of the deflected light beam between the imaging reflecting mirror having an imaging function and the anamorphic lens, and the imaging reflecting mirror and the lens. It has a mirror, and has a function of making the position of the starting point of the deflection by the optical deflector and the position of the surface to be scanned into a geometrical-optical conjugate relationship in the sub-scanning corresponding direction.

The "optical scanning image forming unit" is formed by "superimposing and integrating the image forming reflecting mirror and the anamorphic lens in the image forming optical system in the sub scanning corresponding direction". Of the anamorphic lens, the side surface in the sub-scanning corresponding direction, which is longer in the main-scanning corresponding direction, is referred to as the “attachment reference surface”.

When two long and short optical elements are integrated as described above, the mounting accuracy can be easily increased by mounting with the longer element as a reference.

There are two side surfaces in the direction corresponding to the sub-scan, and either of these two surfaces can be used as a mounting reference surface. The side surface at the part between the image reflector and the anamorphic lens is used as the mounting reference surface.

With this configuration, the reference surface is located outside both ends in the longitudinal direction of the "imaging element shorter in the main scanning corresponding direction" in the main scanning corresponding direction, and the area of the reference surface is smaller, so that the reference surface of the reference surface is smaller. Easy to get accuracy.

The image forming mirror and the anamorphic lens are
They may be formed of the same or different materials, and these may be integrated by adhesion or the like, but these may be “molded products made of the same resin”.

In this case, the imaging reflecting mirror and the anamorphic lens can be "integrated via a rib structure" (claim 3), and in this case, "the imaging reflecting mirror and the anamorphic lens are integrated. The surface of the dividing rib structure "can be used as the attachment reference surface (claim 4).

When the image forming unit for optical scanning is integrated as a mold product, the mold for forming the reflecting surface of the image forming mirror and the mold for forming the lens surface of the anamorphic lens are different from each other. Although it is a mold, if the rib structure is interposed between the imaging reflecting mirror and the anamorphic lens, the two molds can be used separately from each other.

The rib structure is not limited to being provided between the imaging reflecting mirror and the anamorphic lens, but the imaging reflecting mirror and the anamorphic lens can be surrounded by the rib structure (claim 5). By doing so, it is possible to effectively prevent the deformation of the imaging reflecting mirror and the anamorphic lens.

The optical scanning image forming unit, which is a resin-molded product, is easily deformed by the influence of temperature and humidity, and the deformation is most prominent in the main scanning corresponding direction which is the longitudinal direction.

In this case, it is possible to have an "engaging portion for positioning reference in the main scanning corresponding direction" at the central portion in the longitudinal direction of the side edge portion along the longitudinal direction of the imaging reflecting mirror or the anamorphic lens. 6). When the reference engaging portion is provided in the central portion in the longitudinal direction as described above, deformation due to temperature and humidity can be released to both ends in the longitudinal direction.

Of the imaging reflecting mirror and the anamorphic lens, the rib structure along the longitudinal direction, which is longer in the main scanning corresponding direction, has "reference planes for positioning in the optical axis direction" on both side edges in the longitudinal direction. (Claim 7)

The order of the optical arrangement on the optical path from the optical deflector to the surface to be scanned may be either the imaging reflecting mirror or the anamorphic lens first, but the imaging reflecting mirror is provided on the optical path of the deflected light beam. It is possible to arrange the optical scanning imaging unit in the same housing as the optical deflector so as to be located near the optical deflector (claim 8).

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments will be described below.

In FIG. 1 showing the first embodiment of the present invention, reference numeral 4 is a polygon mirror as an optical deflector, which is rotationally driven by a motor 40 as in FIG.

The imaging reflecting mirror indicated by reference numeral 51 has an anamorphic lens 57 and a sub-scanning corresponding direction (vertical direction in FIG. 1).
The two are integrated in a state of being overlapped with each other to form an “optical scanning image forming unit”. Reference numeral 50 indicates an optical scanning imaging unit. The mirror denoted by reference numeral 60 is for bending the optical path of the deflected light beam between the imaging reflecting mirror 51 and the lens 57.

The deflected light beam deflected by the polygon mirror 4, which is an optical deflector, is reflected by the imaging reflecting mirror 51 toward the mirror 60 (therefore, the optical axis of the reflecting surface of the imaging reflecting mirror 51 is a sub-axis). The lens 5 is anamorphic when it is reflected by the mirror 60.
After passing through 7, the light is focused as a light spot on the photoconductor 8 whose generating line coincides with the surface to be scanned, and the photoconductor 8 is optically scanned.

A light beam from a light source not shown in FIG. 1 is converted into a parallel light beam or a divergent or convergent light beam by a coupling lens (not shown in FIG. 1) as in FIG. It is converged by the lens (not shown in FIG. 1) in the sub-scanning corresponding direction, is imaged as a long line image in the main scanning corresponding direction in the vicinity of the deflecting reflection surface of the polygon mirror 4, and is deflected by the polygon mirror 4.

The image forming reflecting mirror 51, the anamorphic lens 57 and the mirror 60 form an "image forming optical system", and the origin of deflection by the polygon mirror 4 and the position of the surface to be scanned are geometrically optics in the sub scanning corresponding direction. And the conjugate relation.

Therefore, in this optical arrangement, the image forming reflecting mirror 51 is close to the polygon mirror 4 which is an optical deflector on the optical path of the deflected light beam, and the scanning image forming unit 50 is incorporated in the same housing as the polygon mirror 4. (Claim 8).

That is, the "housing" is the housing body 7
1 and a lid 72, the polygon mirror 4 is attached to the housing body 71 by a driving motor 40, and the optical scanning imaging unit 50 is also attached to the housing body 71.

In addition to the housing body 71, the mirror 60
Also, a light source, a coupling lens, a cylinder lens, etc., which are not shown, are attached, and by engaging the lid 72 with the housing body 71, these are housed inside the housing.

Therefore, in this embodiment, the optical system for optical scanning is unitized as a whole, and it suffices to install the optical system in alignment with the photoconductor 8.

A window 73 is provided in the housing body 71, and the deflected light beam that has passed through the anamorphic lens 57 is emitted from the window 73. The window 73 may be "plain",
It may be closed with a suitable dustproof glass.

In comparison with FIG. 4, the imaging reflecting mirror 51 has a "function of converging the deflected light beam on the surface to be scanned in the main scanning corresponding direction", and the anamorphic lens 57 is
It has a function of condensing the deflected light flux on the surface to be scanned together with the imaging reflecting mirror 51, and therefore the optical scanning imaging unit 50 has a function of correcting the surface tilt of the polygon mirror 4.

FIG. 2 is an exploded perspective view showing the optical scanning image forming unit 50 in the embodiment shown in FIG. 1 and a portion of the housing body 71 where the optical scanning image forming unit 50 is installed.

The "deflection width" of the deflected light beam is proportional to the distance on the optical path from the origin of deflection. In the embodiment shown in FIG. 1, since the image forming reflecting mirror 51 is closer to the polygon mirror 4 which is an optical deflector than the lens 57 on the optical path, the deflected light beam is covered, so that the main scanning in the longitudinal direction is performed. The length in the corresponding direction of the anamorphic lens 57 is longer than that of the imaging reflecting mirror 51.

Therefore, in this embodiment, the side surface portion in the sub scanning corresponding direction of the lens 57, which is the longer one of the imaging reflecting mirror 51 and the anamorphic lens 57 in the main scanning corresponding direction, is used as the attachment reference surface. 2).

As shown in FIG. 2, the optical scanning unit 50.
Has a rib structure 53 between the imaging reflecting mirror 51 and the anamorphic lens 57 (claim 3), and the lens 57 has an imaging reflection due to the rib structures 53 and 54 and the rib structures at both ends in the longitudinal direction. The mirror 51 has a rib structure 53, 55.
And is surrounded by rib structures at both ends in the longitudinal direction (claim 5).

In FIG. 2, both end sides in the longitudinal direction of the lower surface of the rib structure 53 (the surface integrated with the imaging reflecting mirror 51) are formed with high accuracy as attachment reference surfaces A and A '. (Claims 2, 4, and 5).

Corresponding to the mounting reference planes A and A ', receiving surfaces A1 and A1' are formed with high precision on the housing body 71 side.

Therefore, when the optical scanning image forming unit 50 is assembled to the housing body 71, the mounting reference surfaces A and A'are simply brought into contact with the receiving surfaces A1 and A1 ', respectively. The position of 50 in the sub-scanning corresponding direction can be correctly aligned.

In this way, the outer surface of the rib structure 54 (the upper surface in FIG. 2) can be used as the mounting reference surface for the alignment in the sub-scanning corresponding direction, but the outer surface of the rib structure 54 is large. , Rather than forming this entire surface with high precision,
As described above, it is easier to obtain accuracy when using a portion having a small area such as the mounting reference planes A and A '.

As shown in FIG. 2, at the central portion in the longitudinal direction of the rib structure 55 forming the side edge portion along the longitudinal direction of the imaging reflecting mirror 51, there is an "engaging portion for positioning reference" in the main scanning corresponding direction. A protrusion 56 is provided so as to engage with an engagement hole 76 formed in the housing body 71.

For this engagement, as shown in FIG. 3, a protrusion 76 'is provided on the housing body 71 side, and a recess 56' for engaging with this is provided in the rib structure 55 as an engaging portion for positioning reference. good.

When the image forming unit for optical scanning is thus engaged with the housing at the central portion in the main scanning corresponding direction, the deformation due to temperature and humidity can be released to both ends in the longitudinal direction as described above. The stress applied to the lens surface and the reflection surface due to the deformation can be effectively reduced.

Returning to FIG. 2, "longitudinal edges of the rib structure 54 along the longitudinal direction of the lens 57, which is the longer one of the imaging reflecting mirror 51 and the anamorphic lens 57 in the direction corresponding to the main scanning, is marked with" The reference planes B and B'for "positioning in the optical axis direction" are formed with high precision.

Further, in the housing main body 71, the portions abutting against the reference surfaces B and B'are receiving surfaces B1 and B1 '.
Is formed with high precision.

Therefore, the alignment of the optical scanning imaging unit 50 in the optical axis direction is completed only by bringing the reference surfaces B and B ′ into contact with the receiving surfaces B1 and B1 ′, respectively.

Therefore, as described above, only by mounting the optical scanning image forming unit 50 on the housing main body 71, the optical scanning image forming unit 50 can be operated in the main / sub scanning corresponding direction and the optical axis direction (in the above-described form, the Positioning in the direction of the optical axis 57) is automatically performed.

[0051]

As described above, according to the present invention, in the optical scanning device using the image forming optical system including the image forming reflecting mirror and the anamorphic lens, the assembly of the optical system becomes easy, and The compactness of the optical scanning device can be effectively utilized by superimposing and integrating the image reflecting mirror and the anamorphic lens in the sub-scanning corresponding direction.

According to the second and fourth aspects of the invention, since the area of the mounting reference surface is small, it can be easily formed with high accuracy, and highly accurate alignment in the sub-scanning corresponding direction can be easily realized.

According to the third and fifth aspects of the invention, since separate dies for forming the reflecting surface of the imaging reflecting mirror and the lens surface of the anamorphic lens can be used separately by the rib structure, the accuracy of each surface can be facilitated. Can be increased.

According to the fifth aspect of the present invention, even though the imaging reflecting mirror and the anamorphic lens are long in the direction corresponding to the main scanning, the imaging reflecting mirror and the anamorphic lens are both surrounded by the rib structure, so that the connection is achieved. Deformation such as twisting does not occur on the image reflecting mirror or anamorphic lens.

According to the sixth aspect of the invention, the stress applied to the unit can be effectively reduced by allowing the deformation of the image forming unit for light scanning formed of resin due to temperature and humidity to escape to both sides in the longitudinal direction.

According to the seventh aspect of the present invention, it is possible to easily and surely position the optical scanning image forming unit in the optical axis direction.

According to the eighth aspect of the present invention, the optical scanning device can be made compact by incorporating the optical scanning imaging unit in the same housing as the optical deflector, and the optical scanning device can be easily assembled. .

[Brief description of drawings]

FIG. 1 is a diagram for describing one embodiment of the present invention.

FIG. 2 is an exploded perspective view showing an assembly portion of the image forming unit for optical scanning in the form of FIG. 1 to the housing body.

FIG. 3 is a diagram showing only a characteristic part of a modified example of the form of FIG.

FIG. 4 is a view showing an optical scanning device conventionally used as an optical scanning device using an imaging reflecting mirror.

[Explanation of symbols]

 4 Polygon Mirror (Optical Deflector) 50 Optical Scanning Imaging Unit 51 Imaging Reflecting Mirror 57 Anamorphic Lens 53 Rib Structure 60 Mirror 71 Housing Body

Claims (8)

[Claims] 1. An optical scanning device for performing optical scanning on a surface to be scanned by condensing a light beam deflected by an optical deflector as a light spot on the surface to be scanned by an imaging optical system, and having an imaging function. An image reflecting mirror and an anamorphic lens, and a mirror that bends the optical path of the deflected light flux between the image forming reflecting mirror and the lens are provided. In the image forming optical system having a geometrical optical conjugate relationship in the scanning corresponding direction, the image forming reflecting mirror and the anamorphic lens are overlapped and integrated in the sub scanning corresponding direction, and the image forming reflecting mirror and the anamorphic lens are integrated. An optical scanning imaging unit, wherein a side surface portion in the sub-scanning corresponding direction, which is longer in the main-scanning corresponding direction, is used as a mounting reference surface. 2. The scanning imaging unit according to claim 1, wherein the mounting reference surface is located between the integrated imaging reflecting mirror and the anamorphic lens. . 3. The imaging unit for optical scanning according to claim 1 or 2, wherein the imaging reflecting mirror and the anamorphic lens are mold products made of resin, and the imaging reflecting mirror and the anamorphic lens have a rib structure. An image forming unit for optical scanning, characterized by being integrated via. 4. The optical scanning image forming unit according to claim 3, wherein a surface of a rib structure for separating the image forming reflecting mirror and the anamorphic lens is a mounting reference plane. 5. The optical scanning image forming unit according to claim 4, wherein both the image forming reflecting mirror and the anamorphic lens are surrounded by a rib structure. 6. The optical scanning image forming unit according to claim 3, 4 or 5, wherein the image forming reflecting mirror or the anamorphic lens is provided with a main scanning direction in a central portion of a side edge portion along the longitudinal direction in the longitudinal direction. An image forming unit for optical scanning, comprising an engaging portion for positioning reference. 7. An optical scanning imaging unit according to claim 3, 4 or 5 or 6, wherein a rib structure of the imaging reflecting mirror and the anamorphic lens, which is longer in the main scanning corresponding direction, extends along the longitudinal direction. An optical scanning image forming unit, which has reference surfaces for positioning in the optical axis direction on both side edges in the longitudinal direction of. 8. The optical scanning imaging unit according to claim 1, 2 or 3 or 4 or 5 or 6 or 7, wherein the imaging reflecting mirror is close to the optical deflector on the optical path of the deflected light beam. An image forming unit for optical scanning, which is incorporated in a housing common to the above.