JP2005010358A - Optical scanner and tandem type image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the deviation of an image on respective photoreceptors due to a scanning line curve as far as possible with a low cost and a simple structure. <P>SOLUTION: In a counter scanning type optical scanner having a first optical path with which the photoreceptor 4a is scanned with a light beam emitted from a light source 6a and deflected with a rotary deflector 1 and a second optical path with which the photoreceptor 4b is scanned with a light beam emitted from a light source 6b and deflected with a rotary deflector 1, scanning lenses 2a and 2b are arranged on both sides of the rotary deflector 1, the photoreceptor 4a is scanned with the light beam passing through the scanning lens 2a via a reflection member 3a and the photoreceptor 4b is scanned with the light beam passing through the scanning lens 2b via two reflection members 3b and 3c. Thus, the directions of the scanning line curves can be aligned. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical scanning device and a tandem type image forming apparatus used for a color laser printer or a color digital copying machine.
[0002]
[Prior art]
4 is a schematic view showing a conventional counter scanning type optical scanning device, FIG. 5 is a plan view showing a configuration in the vicinity of the rotary deflector in FIG. 4, 1 is a rotary deflector, 2a and 2b are scanning lenses, 3a, 3b is a reflecting member, 4a and 4b are photosensitive members, 5 is a transfer belt, 6a and 6b are light sources, and 7 is a housing.
[0003]
Scanning lenses 2a and 2b and reflecting members 3a and 3b are provided on both sides of one rotary deflector 1, and the scanning lens 2a and the scanning lens 2b, and the reflecting member 3a and the reflecting member 3b are the same member. The photoconductors 4a and 4b are arranged in contact with a transfer belt 5 stretched by two roller bodies so as to be circulated. The rotary deflector 1 is disposed between the photoconductor 4a and the photoconductor 4b. The scanning lenses 2a and 2b, the reflecting member 3a, and the reflecting member 3a are arranged at substantially symmetrical positions with the rotation center axis of the rotary deflector 1 as the axis of symmetry. 3b and photoreceptors 4a and 4b are arranged. The rotary deflector 1, the scanning lenses 2a and 2b, the reflecting members 3a and 3b, and the light sources 6a and 6b are attached to the housing 7 and configured as a unit body.
[0004]
The laser light emitted from one of the light sources 6a is deflected by the rotary deflector 1, and the deflected light becomes light that can obtain a predetermined beam spot diameter on the photosensitive member 4a by the scanning lens 2a, and is reflected by the reflecting member 3a. By being deflected toward the photoconductor 4a, the photoconductor 4a is scanned with the beam light. Hereinafter, the optical path until the laser light emitted from the light source 6a reaches the photoconductor 4a is referred to as a first optical path. The laser light emitted from the other light source 6b is irradiated toward a deflecting surface other than the surface that deflects the laser light emitted from the light source 6a in the rotary deflector 1, and is exposed through the scanning lens 2b and the reflecting member 3b. By being guided to the body 4b, the photosensitive body 4b is scanned with the beam light. Hereinafter, the optical path until the laser light emitted from the light source 6b reaches the photosensitive member 4b is referred to as a second optical path.
[0005]
In addition, as this type of conventional technology, there are technologies described in Patent Documents 1 to 3.
[0006]
In Patent Document 1, in an optical writing device of an image forming apparatus, a scan line curve that occurs when a long lens is used is easily adjusted, and correction is made so that the scan line curves match among a plurality of light beams. Thus, a technique for preventing the occurrence of color misregistration is described.
[0007]
Patent Document 2 describes a technique that enables stable bow adjustment.
[0008]
Patent Document 3 describes a beam scanning device that can suppress degradation of a reproduced image while using a resin lens.
[0009]
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-148551 [Patent Document 2]
JP 2002-311361 A [Patent Document 3]
Japanese Patent Laid-Open No. 11-2766
[Problems to be solved by the invention]
In recent years, resin lenses are often used because of their merit of being inexpensive and capable of forming free-form surfaces. However, due to internal distortion during molding and non-uniformity in mold temperature, the focal curve is more than that of glass lenses. , Will be more noticeable.
[0011]
On the other hand, as shown in FIG. 4, a so-called counter scanning optical system that performs exposure scanning on a plurality of photoconductors simultaneously is known as a prior art.
[0012]
With respect to this counter scanning optical system, in the prior art, for example, as shown in Patent Document 1, in order to make this scanning line curve uniform on each photoconductor, there is also a means provided with an adjustment mechanism inside the scanning optical system. As is known, there is a problem that the number of adjustment steps increases and the number of parts associated with the adjustment mechanism increases, resulting in an increase in cost.
[0013]
Further, as a merit of the counter scanning optical system, it is not necessary to provide a rotating deflector corresponding to each photoconductor, and a plurality of photoconductors can be exposed and scanned by a single rotary deflector. The point is that it can go down.
[0014]
However, in the conventional counter scanning optical system having no adjustment means for scanning line bending, as shown in FIG. 4, the focal line bending of the scanning lenses 2a and 2b is reversed with respect to the left and right optical systems. There is a possibility that the superposition due to the scanning line bend on each photoconductor becomes twice as much as the actual bend amount and shifts.
[0015]
It is an object of the present invention to provide an optical scanning apparatus and a tandem type image forming apparatus that can reduce image displacement on each photoconductor due to such scanning line bending as much as possible with a low-cost and simple configuration. And
[0016]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 is provided corresponding to a plurality of light sources that generate light beams, a rotary deflector that deflects and scans the light beams from these light sources, and a plurality of light sources. A scanning lens for imaging the laser beam deflected by the rotary deflector so that a predetermined beam spot diameter is obtained on the photosensitive member, and light transmitted through the scanning lens on the photosensitive member corresponding to the light source A plurality of scanning lenses corresponding to a plurality of photoconductors, wherein the plurality of scanning lenses are arranged so as to be substantially line symmetric with respect to an axis of symmetry passing through the center of the rotary deflector. In the counter scanning type optical scanning apparatus that outputs and scans the photosensitive members by exposure scanning, the number of the reflecting members after one scanning lens in the pair of scanning lenses is an odd number and the number after the other scanning lens in front The number of reflecting members, characterized in that the even number. With such a configuration, the direction of the scanning line curve on the photoconductor exposed and scanned by the optical scanning device can be aligned in the same direction on each photoconductor. In addition, since the scanning line curve corresponding to each photoconductor can be made uniform, even when a resin molded lens having a relatively large focal line curve is employed, the scanning line curve can be made uniform.
[0017]
The invention according to claim 2 is characterized in that, in the invention according to claim 1, the reflecting member is one sheet on one photoconductor side and two sheets on the other photoconductor side. With such a configuration, the number of reflecting members constituting the optical scanning device can be minimized, and the number of parts can be reduced and the cost can be reduced.
[0018]
The invention according to claim 3 is characterized in that, in the invention according to claim 1 or 2, the pair of scanning lenses is the same lens having power in the sub-scanning direction. With such a configuration, the scanning line bending amount in each scanning lens can be made equal, so that it is possible to reduce the positional deviation of the scanning line on the photosensitive member.
[0019]
The invention according to claim 4 is characterized in that, in the invention according to claim 1, 2, or 3, the mounting portions of the pair of scanning lenses have the same shape. With such a configuration, in the pair of scanning lenses, it is possible to equalize the amount of bending of the scanning line caused by the influence of internal distortion during molding, mold temperature non-uniformity, and the like.
[0020]
The invention according to claim 5 is the invention according to any one of claims 1 to 4, wherein the scanning lens is a resin molded product. With such a configuration, the cost for the scanning lens can be reduced.
[0021]
According to a sixth aspect of the invention, a plurality of optical scanning devices according to any one of the first to fifth aspects, a plurality of photosensitive members provided corresponding to the respective optical scanning devices, and exposure scanning by the respective optical scanning devices. And a means for sequentially transferring an image formed by attaching a developer to the latent image formed on each photoconductor onto a sheet. With such a configuration, it is possible to configure a full-color tandem image forming apparatus capable of simultaneously printing four colors of black, magenta, yellow, and cyan, and furthermore, it is possible to uniformly align the scanning line curve. It becomes possible to obtain a high-quality printing result that prevents the occurrence of color misregistration.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0023]
FIG. 1 is a schematic diagram showing an opposed scanning optical scanning device according to an embodiment of the present invention, FIG. 2 is a schematic diagram showing a focal curve of a scanning lens, and 3c is a reflecting member. 4 and 5, the same members or members having the same functions as those in the prior art shown in FIG. 4 are denoted by the same reference numerals, and detailed description thereof is omitted.
[0024]
In the present embodiment, a reflecting member 3c is provided on the second optical path in the prior art shown in FIG. 4, and the laser light emitted from the light source 6b is deflected by the rotary deflector 1 as shown in FIG. Then, the deflected light becomes light that can obtain a predetermined beam spot diameter on the photosensitive member 4b by the scanning lens 2b, is deflected to the reflecting member 3c side by the reflecting member 3b, and further deflected to the photosensitive member 4b side by the reflecting member 3c. As a result, the photosensitive member 4b is scanned with the beam light.
[0025]
FIG. 1 shows a lens having power in both main and sub scanning lenses 2a and 2b, for example, a curved toroidal lens. However, as an embodiment of the present invention, a single lens (= single lens) is shown. Lens). In other words, since the influence of the scanning lens on the focal line is dominated by the lens having power in the sub-scanning direction, for example, in the case of a scanning lens using a combination of an fθ lens and a toroidal lens, a toroidal lens is used. Only need to be considered.
[0026]
Next, the focal curve of the scanning lens will be described in detail.
[0027]
First, as shown in FIG. 2A, it is assumed that the focal line bends of the scanning lenses 2 a and 2 b are convex upward with respect to the mounting seat surface of the scanning lenses 2 a and 2 b in the housing 7. In this case, when the light beams from the scanning lenses 2a and 2b are viewed facing each other, the scanning line immediately after passing through the scanning lenses 2a and 2b scans upward along the lenses as shown in FIG. It becomes a line and is led to the reflecting member.
[0028]
In the prior art, as shown in FIG. 4, the rotating deflector 1 is disposed so as to be sandwiched between substantially the intermediate positions of the photoconductors 4a and 4b. Therefore, the scanning line bending on the photoconductors 4a and 4b is not caused. When viewed from the rotary deflector 1, the right side and the left side have different (reverse) directions. As a result, the printed image is displaced by twice as much as the actual amount of bending of the scanning line, resulting in extremely poor image deterioration.
[0029]
On the other hand, according to the present embodiment, the number of reflecting members on the first optical path is set to one, and the number of reflecting members on the second optical path is set to two. Since the scanning line curve is plane-symmetric with respect to the scanning line curve on the photosensitive member 4b shown in FIG. 4, the convex direction of the scanning line can be matched. That is, by setting the number of reflecting members on one optical path to an odd number and the number of reflecting members on the second optical path to an even number, the direction of scanning line bending caused by the focal line bending of the scanning lens Can be aligned in the same direction on the printed image. As described above, according to the present embodiment, it is possible to make the scanning line bends on the respective photosensitive members the same and perform good alignment.
[0030]
The scanning lenses 2 a and 2 b provided on the left and right of the rotary deflector 1 are positioned so that the mounting surface of the housing 7 and the focal line are parallel to each other, and the mounting portions of the scanning lenses 2 a and 2 b in the housing 7 are positioned. Are of the same shape and are line symmetric with respect to the axis of symmetry passing through the rotation axis. Moreover, since they are the same lens, the amount of scanning line bending of the scanning lenses 2a and 2b is substantially the same. As a result, it is not necessary to correct the amount of bending of the scanning line corresponding to each of the photoconductors 4a and 4b, and the apparatus can be simplified and the cost can be reduced.
[0031]
In addition, according to the present embodiment, the number of reflecting members is one on the first optical path and two on the second optical path with respect to one rotary deflector, thereby reducing the number of reflecting members. As a result, the number of parts can be reduced and the cost can be greatly reduced. In this embodiment, even if the focal line curve of the scanning lenses 2a and 2b is relatively large, the scanning line curve can be uniformly aligned with respect to each of the photoconductors 4a and 4b. Can be adopted.
[0032]
FIG. 3 is an explanatory view showing an image forming apparatus provided with two sets of the opposed type optical scanning device shown in FIG. 1, wherein 4c and 4d are photosensitive members, 10 and 11 are optical scanning devices, and 12 is a developing device. 4 and 5, the same members or members having the same functions as those in the prior art shown in FIG. 4 are denoted by the same reference numerals, and detailed description thereof is omitted.
[0033]
On the transfer belt 5, a photoconductor 4a, a photoconductor 4b, a photoconductor 4c, and a photoconductor 4d are arranged in parallel in this order, and an optical scanning device 10 is arranged between the photoconductor 4a and the photoconductor 4b. An optical scanning device 10 is disposed between the body 4c and the photoreceptor 4d. The optical scanning device 10 and the optical scanning device 11 have the same configuration, and are configured by the rotary deflector 1, the scanning lenses 2a and 2b, and the reflecting members 3a, 3b, and 3c shown in FIG.
[0034]
This makes it possible to make the scanning line curve uniform for the four photoconductors. For example, the developer of the developing device 12 corresponding to the photoconductors 4a, 4b, 4c, and 4d is black, magenta, yellow, Tandem image formation capable of simultaneously printing four colors by superimposing images formed on the surfaces of the photoreceptors 4a, 4b, 4c, and 4d on paper conveyed by the transfer belt 5 with four colors of cyan The apparatus can be configured, and it is possible to configure a full-color image forming apparatus that suppresses image deterioration due to the shift of the scanning line with an inexpensive and simple configuration.
[0035]
【The invention's effect】
As described above, according to the present invention configured as described above, the direction of the scanning line curve on the photoconductor exposed and scanned by the optical scanning device can be aligned in the same direction on each photoconductor. By using the scanning lens, the amount of bending of the scanning line can be made equal, so that the positional deviation of the scanning line on the photosensitive member can be reduced.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a counter scanning optical scanning device according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing focal line bending of a scanning lens. FIG. 4 is a schematic diagram showing a conventional counter-scanning optical scanning device. FIG. 5 is a plan view showing the configuration near the rotary deflector in FIG.
DESCRIPTION OF SYMBOLS 1 Rotating deflector 2a, 2b Scan lens 3a, 3b, 3c Reflective member 4a, 4b, 4c, 4d Photoconductor 5 Transfer belt 6a, 6b Light source 7 Housing 10, 11 Optical scanning device

Claims (6)

A plurality of light sources that generate light beams, a rotary deflector that deflects and scans the light beams from these light sources, and a laser beam that is provided corresponding to the plurality of light sources and that is deflected by the rotary deflectors on the photoreceptor. A scanning lens that forms an image so as to obtain a predetermined beam spot diameter, and a reflecting member that guides the light transmitted through the scanning lens to an optical writing position on a photoconductor corresponding to the light source, A pair of the scanning lenses are arranged so as to be substantially line symmetric with respect to an axis of symmetry passing through the center of the rotary deflector, and a plurality of light beams corresponding to the plurality of photoconductors are output to expose and scan each photoconductor. In a scanning optical scanning device,
An optical scanning device characterized in that in the pair of scanning lenses, the number of reflecting members after one scanning lens is an odd number, and the number of reflecting members after the other scanning lens is an even number. 2. The optical scanning device according to claim 1, wherein the number of the reflecting members is one after one scanning lens and two after the other scanning lens. 3. The optical scanning device according to claim 1, wherein the pair of scanning lenses are the same lens. 4. The optical scanning device according to claim 1, wherein the mounting portions of the pair of scanning lenses have the same shape. The optical scanning device according to claim 1, wherein the scanning lens is a resin molded product. A plurality of optical scanning devices according to any one of claims 1 to 5, a plurality of photosensitive members provided corresponding to the respective optical scanning devices, and exposure scanning by each optical scanning device. A tandem type image forming apparatus comprising: means for sequentially transferring an image formed by attaching a developer to the latent image onto a sheet;

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