JP2003315719A - Optical scanner and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical scanner having an optical performance which can be secured and stabilized without the production of a remarkably accurate shape by constituting an optical scanning system without using an incident mirror, and also, having a simple constitution and an easy assemblage, and to provide an image forming apparatus equipped with the optical scanner. <P>SOLUTION: The optical scanner is provided with several light sources and an optical deflector (5) for performing optical-scanning, several light beams separated with leaving a distance A in a sub scanning direction are deflected by the optical deflector (5), two light sources (6a and 6b) among the several light sources are arranged with leaving a distance B longer than the distance A in the subscanning direction, and the optical scanner is provided with an optical path changing means (P) on one or both optical paths of light emitted from the two light sources (6a and 6b) so as to change the optical path by reflecting or refracting the light once or more times and changing a distance between two optical paths from the distance B to the distance A. <P>COPYRIGHT: (C)2004,JPO

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 for color images such as a laser printer, a laser facsimile, and a digital PPC copying machine, and an image forming apparatus equipped with the same.

[0002]

2. Description of the Related Art With the recent color image formation of image forming apparatuses, scanning light is made incident on a plurality of image carriers represented by a four-tandem tandem arrangement as disclosed in Japanese Patent No. 2725067. Things to do are being devised and commercialized. As a scanning optical system corresponding to such a tandem type image forming unit, it is also described in the above-mentioned Japanese Patent No. 2725067, but a polygon motor, which is one of the most expensive parts, is used in common as much as possible. The number of devices and products that are designed and implemented in an attempt to secure high reliability through system cost reduction, size reduction, and simplification are increasing.

FIG. 7 is a schematic diagram showing an example of a color image forming apparatus, (a) is a plan view and (b) is a central sectional view. The optical scanning device 2 located inside the image forming apparatus 1 includes an optical housing 3 for mounting an optical element at a predetermined position, a housing cover 4 that blocks the inside of the optical housing 3 from the outside and performs a dustproof and soundproof function. , A rotary polygon mirror (hereinafter referred to as “polygon mirror”) 8, an optical deflecting device 5, a laser oscillation unit 6, and a plurality of optical elements. The light flux reflected by the polygon mirror 8 passes through the fθ lens 9 and the long lens 10, passes through the dustproof glass 11, and reaches the photoconductor 12. With the rotation of the polygon mirror 8, the light beam scans the surface of the photoconductor 12 in a straight line to form an electrostatic latent image, and an image is formed through an image forming process.

The image forming apparatus shown in FIG. 7 is provided with two photoconductors 12a and 12b, which are optically scanned by the optical scanning device 2 with the optical paths of the two light fluxes corresponding to them. First, in the first optical path reaching the photoconductor 12a, the light beam emitted from the laser oscillation unit 6a passes through the cylindrical lens 7a and is irradiated onto the upper side of the two-stage polygon mirror 8. Further, in the second optical path reaching the photoconductor 12b, the light beam emitted from the laser oscillation unit 6b passes through the cylindrical lens 7b, is then folded back by the incident mirror M, and is irradiated to the lower side of the two-stage polygon mirror 8. To be done. The arrangement of the light source in the sub-scanning cross-section direction is such that the first optical path from the laser oscillation unit 6a to the polygon mirror 8 and the second optical path from the laser oscillation unit 6b are parallel to each other with a certain distance. There is.
The fθ lens 9 has upper and lower optical paths that pass in parallel with each other, and has upper and lower two-stage lens surfaces so as to have a lens effect on each light flux. After that, the light beam of the first optical path is reflected by the mirror 13a and the long lens 10.
a, the mirror 14, and the dust-proof glass 11a, and reaches the photoreceptor 12a on the left side. The light beam of the second optical path passes through the long lens 10b, the mirror 13b, and the dustproof glass 11b, and reaches the photoconductor 12b on the right side.

A color image is generally formed by superposing four color toner images of black, magenta, yellow and cyan. In the image forming apparatus of FIG. 7, first, an electrostatic latent image is formed on the photoconductor 12a by the first light beam, and a toner image is formed by the black developing section 15a.
Further, an electrostatic latent image is formed on the photoconductor 12b by the second light beam at a constant interval, and the magenta developing unit 1
In 5b, a magenta toner image is formed. The two toner images are transferred onto the intermediate transfer belt 17 so that their positions are aligned with each other. Next, the first light beam is applied again to the photoconductor 12
A yellow electrostatic latent image is formed on a, and the yellow developing unit 1
A toner image is formed at 6a. Similarly, a cyan toner image is formed on the photoconductor 12b by the second light beam at a fixed interval in the cyan developing unit 16b. The intermediate transfer belt 17 makes one rotation after the previous step, and the toner images of these two colors are superimposed and transferred onto the two colors transferred previously. The color image formed in this way is transferred to the transfer paper at the secondary transfer unit 18, and a hard copy is obtained.

FIG. 8 is a diagram showing an example of the configuration of the laser oscillation unit 6a or 6b. The laser oscillation unit is LD 61, LD base 62, collimator lens 6
3, an aperture 64, and an LD control plate 65. L
D61 is press-fitted into a fitting hole provided in the LD base 62. The LD base 62 is integrally provided with a pedestal 66 that supports the collimator lens 63. The collimator lens 63 is fixed on the pedestal 66 with an adhesive or the like so that the laser light emitted from the LD 61 has a target optical axis and is parallel to the target optical axis. The aperture 64 is press-fitted and attached to the LD base 62 so as to wrap the pedestal 66 and the collimator lens 63, and shapes the beam shape so that the laser light has an appropriate shape for the rear optical system. L
The D control plate 65 is fixed to the LD base 62 with a screw 67, and is electrically coupled to the lead wire 68 of the LD by soldering.

As an example of a method of fixing the collimator lens 63, an adjusting process using a collimator adjusting device will be described. L
The D base 62 is accurately fixed to a predetermined position of the collimator adjusting device by a fixing jig. Next, the collimator lens 63 is grasped by the adjustment clamp which is movable and rotatable in the X, Y, Z, α, and β directions. An ultraviolet curable adhesive is filled between the collimator lens 63 and the pedestal. A light beam is generated and the position and parallelism thereof are detected by a light receiving element installed at a predetermined distance, and the clamp is moved to adjust the collimator lens 63 to an appropriate position. In this state, ultraviolet rays are irradiated from the edge of the collimator lens 63 to cure the adhesive, and the adjustment and fixing of the collimator lens 63 are completed. This bonding method is disclosed in JP-A-9-24396.
This is the method disclosed in Japanese Patent No.

FIG. 9 is a view showing a conventional method of supporting the entrance mirror M which is often used. Generally, in order to three-dimensionally determine the attitude of the reflecting surface of the mirror, any three points may be brought into contact with the reflecting surface and urged. In FIG. 9, the contact portions 21, 22, and 23 installed in the optical housing 3 are biased. It is the positional accuracy of each of the contact portions 21 and 22 arranged vertically in FIG. 9 that determines the inclination β of the entrance mirror M when viewed from the sub-scanning cross-sectional direction.
Further, it is the positional accuracy of the contact portion 23 with respect to the contact portions 21 and 22 that determines the inclination α when viewed from the main scanning cross section direction. In addition, the vertical positioning of the entrance mirror M is performed by abutting at two abutting portions 25 provided on the optical housing 3, similarly to the abutting portion described above. However, this vertical positioning is performed with respect to the end surface of the entrance mirror M, and in terms of required positional accuracy, the above-mentioned three points are brought into contact with each other to attach the posture of the reflecting surface of the mirror M. It is possible to set a tolerance that is one order lower than the case where it is used. These contact portions support two biasing members 24 such as a leaf spring that supports and presses the biased incident mirror M.
Are installed corresponding to the front and rear abutting portions. Although omitted here, the positioning of the entrance mirror M in the front-rear direction may be performed as described above.

Now, the problem relating to the inclination β of the incident mirror M in the sub-scanning direction in the scanning optical system using the incident mirror M will be described below. FIG. 10 is a vertical cross-sectional view of the entrance mirror M. For example, as shown in FIG. 10, it is assumed that the entrance mirror M is installed so as to be inclined by Δβ from the originally set attitude (vertical in this case). Then, due to the law of reflection in the mirror, the light flux reaching the polygon mirror (not shown) from the incident mirror M is inclined by 2Δβ. Let L0 be the span of the contact portions 21 and 22, and Δ be the positional accuracy of these,

[Equation 1] Becomes L0 is often about 10 mm due to the cost of the entrance mirror M and the space for installation, and Δ is 0.03 mm even if it is estimated to be the minimum from the manufacturing accuracy of the optical housing that can be mass-produced. ,

[0010]

[Equation 2] Becomes

Next, the influence of Δβ on the above-mentioned entrance mirror M will be described. FIG. 11 is a side view of the arrangement of the optical elements, FIG. 12 is a schematic configuration diagram of the optical scanning device, (a) is a plan view, and (b) is a sectional view. 11,
In FIG. 12, assuming that the optical path length between the incident mirror M and the polygon mirror 8 is L1, the polygon mirror 8 according to the above Δβ.
The deviation h1 in the sub-scanning direction at the reflection point of

[Equation 3] Becomes The light beam reflected by the polygon mirror 8 also has an inclination of 2Δβ, and the deviation in the sub-scanning direction is caused by the long lens 1.
When it reaches the final surface of 0, it becomes h2. If the optical path length from the light deflecting device 5 to the final surface of the long lens 10 is L2,

[0012]

[Equation 4] Is.

By the way, it has been empirically known from an optical calculation that various optical performances are largely deviated from the target unless h2 is kept below about 0.5 mm. Therefore, if this numerical value is substituted into the above equation (2),

[Equation 5] It will be convenient when it comes to. Solving this for Δβ,

[0014]

[Equation 6]

Here, using the values of a certain actually designed scanning optical system, L1 = 60 mm and L2 = 160 mm,
In {} of the above equation (3),

[Equation 7] Therefore, the equation (3) is

[0016]

[Equation 8] Becomes

Comparing the above equations (1) and (4), it is difficult to keep Δβ of the incident mirror M within a range that does not cause a problem, considering the actual mass production process. . Therefore, it is necessary to set the positional accuracy of Δ to a high accuracy of, for example, about 0.01 mm that does not cause a difference in process capability, and a labor such as a local dimension control of the optical housing 3 is required to secure optical performance. I had to spend. Further, the fact that the optical performance sensitively affects Δβ is not preferable even for environmental changes represented by temperature rises inside and outside the optical housing 3, and the scanning light optical characteristics due to thermal expansion and thermal deformation of the optical housing 3. Can be a bigger problem.

[0018]

SUMMARY OF THE INVENTION In view of the above problems, the present invention comprises a scanning optical system without using an incident mirror to ensure optical performance without producing a highly precise shape. It is an object of the present invention to provide an optical scanning device which is stable, has a simple structure and is easy to assemble, and is more effective in compactness, and an image forming apparatus having the optical scanning device.

[0019]

In order to solve the above-mentioned problems, the invention according to claim 1 comprises a plurality of light sources and an optical deflecting device for performing optical scanning. The optical deflecting device comprises: In an optical scanning device for deflecting a plurality of light beams separated by a distance A in the sub-scanning direction, at least two of the light sources have a distance B larger than the distance A in at least the sub-scanning direction.
Of the light beams emitted from the two light sources, or both of them are reflected or refracted one or more times to change the optical path. The optical scanning device includes an optical path changing unit that changes the distance from the distance B to the distance A. A second aspect of the present invention is the optical scanning device according to the first aspect, wherein the optical path changing means is a parallelogram prism. The invention described in claim 3 is the optical scanning device according to claim 1, wherein the optical path changing means is a folding mirror.

According to a fourth aspect of the present invention, in the optical scanning device according to any one of the first to third aspects, the light beams emitted from the plurality of light sources are collected in the sub-scanning direction near the optical deflector. The plurality of optical elements that emit light are an optical scanning device that is integrally formed. The invention according to claim 5 is
The optical scanning device according to any one of claims 1 to 4, wherein at least the two light sources and the optical path changing unit are provided on one subunit. According to a sixth aspect of the present invention, in the optical scanning device according to the fifth aspect, the sub-unit is an optical device that condenses the light beams emitted from the two light sources in the sub-scanning direction in the vicinity of the optical deflector. The optical scanning device includes an element.
The invention according to claim 7 is the optical scanning device according to any one of claims 1 to 6, wherein the optical scanning device is a single substrate for supplying signals and electric power to the plurality of light sources. And an optical scanning device. An eighth aspect of the present invention is an image forming apparatus including a plurality of image carriers therein and the optical scanning device according to any one of the first to seventh aspects.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of an optical scanning device according to the present invention, and is a view in a direction including an optical path of a light beam emitted from a laser oscillation unit 6a. The laser oscillating unit 6a and the laser oscillating unit 6b, which irradiate the light beam to the light deflecting device 5 using the two-stage polygon mirror 8, are arranged at a distance B in the sub-scanning direction. Reference numerals 7a and 7b are cylindrical lenses. Although not shown in this figure, the configuration of other optical elements such as the fθ lens, the long lens, and the dustproof glass may be the same as that of the optical scanning device 2 shown in FIG. 7. The light beam emitted from the laser oscillation unit 6a is a cylindrical lens 7a.
The light flux radiated to the upper side of the polygon mirror 8 through the laser oscillation unit 6b passes through the cylindrical lens 7b and is radiated to the lower side of the polygon mirror 8 as shown in FIG. It is the same. At this time,
The distance A between the light beams incident on the upper and lower stages of the polygon mirror 8 is represented by the distance A. As shown in FIG. 1, the distance B in the sub-scanning direction between the laser oscillating unit 6a and the laser oscillating unit 6b shown above requires a distance greater than the height direction of the laser oscillating unit due to the arrangement of the two. And is larger than the distance A.

The optical scanning device of the present invention comprises the above-mentioned two light sources,
That is, it has an optical path changing means for changing the optical path interval of the light beams emitted from the laser oscillation unit 6a and the laser oscillation unit 6b from the distance B to the distance A. In FIG. 1, as a means for changing the optical path of the light beam from the laser oscillation unit 6b, a prism P having a parallelogram shape is installed at a position in front of the optical path. The light beam emitted from the laser oscillation unit 6b is reflected upward by 90 ° by the prism P and then by 90 ° in the direction of the polygon mirror 8. By these two reflections, the distance between the first optical path from the laser oscillation unit 6a and the second optical path from the laser oscillation unit 6b becomes narrower from the distance B to the distance A, and the second optical path passes through the cylindrical lens 7b. After passing, the lower side of the polygon mirror 8 is irradiated.

FIG. 2 is a layout view of two folding mirrors shown as another embodiment of the optical path changing means. Instead of the prism P, two folding mirrors m1 and m2 are used.
Can also be used. The mirrors m1 and m2 are positioned in the optical housing 3 so as to face each other in parallel at an angle of inclination of 45 °, and are fixed by the leaf springs 30 and 31. The light beam emitted from the laser oscillation unit 6b is reflected upward by 90 ° by the mirror m1 and then by 90 ° in the direction of the polygon mirror 8 by the mirror m2, and the distance from the first optical path from the laser oscillation unit 6a is increased. It passes through the cylindrical lens 7b at an interval of A and reaches the polygon mirror 8.

1 and 2, the optical path changing means for changing the second optical path is shown.
The present invention is not limited to this, and may be one that changes the first optical path, or one that changes both the first optical path and the second optical path. It suffices if the optical path changing means is provided. Also, regarding the optical path changing means, although the embodiment shows that the reflection of 90 ° is performed twice, the reflection angle and the number of times are not limited to this, and the first optical path and the second The distance between the optical path and the optical path may be designed to be narrowed to the distance A. Further, as for the optical element to be used, other than the prism and the folding mirror described above, any optical element having the same function may be used. Further, the optical element may be one that refracts light rays as well as one that reflects light rays.

As described above, with the above configuration, the distance between the first optical path and the second optical path incident on the polygon mirror 8 can be changed to the distance A without using the incident mirror. Further, since the first optical path and the second optical path can be laid out at the same position as viewed from above, the mounting portions of the laser oscillation units 6a and 6b of the optical housing 3 are flush with each other, and a compact and simple shape can be obtained. it can. When the optical housing 3 is resin-molded, it is not necessary to form it in a slanted shape due to the layout of the second optical path.

Next, the cylindrical lens 7 for converging the light beams emitted from a plurality of light sources near the light deflector 5 will be described. FIG. 3 is a perspective view of an integral type cylindrical lens in which two cylindrical lenses are integrated. In the configuration of FIG. 1, the laser oscillation unit 6
Since a and 6b are arranged vertically, the cylindrical lenses 7a and 7b through which the light beams emitted from both pass are also arranged vertically. In FIG. 3, these cylindrical lenses 7a and 7b are integrally formed. When it is made of glass, the two cylindrical lenses are bonded with an adhesive or the like. When it is formed of resin, it can be integrally molded. As a result, the number of parts such as the urging member necessary for installation in the optical housing 3 can be reduced, and in particular, when integrally molded with resin, there is an advantage that the mounting becomes easy. In addition, in FIG.
Although the simple cylindrical lens 7 for condensing the light beam in the sub-scanning direction is shown, the optical element is not limited to this, and is a lens for condensing in the sub-scanning direction in the vicinity of the optical deflector 5. Then you can apply.

FIG. 4 shows two light sources and an optical path changing means in one.
It is the figure comprised by one subunit. LD base 62
Further, each of the LDs 61a and 61b is press-fitted into a fitting hole provided in the LD base 62. The corresponding collimating lenses 63a and 63b are fixed to the upper and lower pedestals 66a and 66b with an adhesive or the like. The aperture 64 with two openings allows these pedestals 66 to
The a and 66b and the collimating lenses 63a and 63b are attached by being inserted in the LD base 62. The prism P, which is an optical path changing unit, is positioned and fixed inside the LD base 62. As described above, by configuring at least two light sources and the optical path changing means by one subunit, the number of parts can be reduced and the structure of the optical housing 3 can be simplified, so that the assembly is facilitated. In addition, the LD control plate 65 includes the LD base 62.
Is fixed to the two LDs 61 by screws 67a and 67b.
By connecting to the lead wires a and 61b by soldering, it is possible to provide a configuration in which signals and electric power are supplied to each light source by this one substrate.

FIG. 5 is a diagram showing a structure in which the above subunit is further provided with a cylindrical lens. Figure 4
LDs 61a, 61b and collimating lens 63 shown in FIG.
By forming the cylindrical lens 7 as one subunit together with a, 63b, the aperture 64, and the prism P which is the optical path changing means, the number of parts can be reduced. Also,
As shown in FIG. 5, the cylindrical lens 7 is formed into a rectangular parallelepiped shape by the resin integral molding so that the outer frame surrounds the lens shape, and is inserted and fixed in the slit formed in the LD base 62. By doing so, it is possible to further reduce the number of parts, contribute to simplification of the structure of the optical housing 3, and facilitate assembly.

The image forming apparatus of the present invention is an image forming apparatus having a plurality of image carriers therein and the optical scanning device described above. The present invention can be applied to an image forming apparatus having two image carriers as shown in FIG. 7 or a so-called tandem type image forming apparatus using four image carriers. It is also possible to use a multi-beam writing method in which a plurality of scanning light beams are applied to each image carrier. FIG. 6 is a diagram showing the structure of a multi-channel LD array.
For example, in the configuration shown in FIG. 4, by using the multi-channel LD array shown in FIG. 6 for the LD 61, the number of light beams in each optical path becomes an integral multiple, which speeds up writing or increases the density, or saves energy. Can be realized.

[0030]

As described above, according to the present invention, one of the light beams emitted from the two light sources arranged above and below with the distance B in the sub-scanning direction,
Alternatively, an optical path changing unit that narrows the optical path distance between the two light beams is provided on both optical paths, so that the optical path distance between the two light beams incident on the optical deflection scanning device can be reduced without using an entrance mirror. Thus, it is possible to provide an optical scanning device capable of changing the interval so as to be incident on the optical deflector and making the incident, and ensuring stable optical performance without producing a particularly highly accurate shape. Further, according to this configuration, the two optical paths from the two light sources can be laid out at the same position when viewed from above, so that the light source unit mounting portion of the optical housing is on the same surface, and a compact and simple shape can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of an optical scanning device according to the present invention.

FIG. 2 is a diagram showing another embodiment of an optical path changing unit.

FIG. 3 is a perspective view of an integral type cylindrical lens in which two cylindrical lenses are integrated.

FIG. 4 is a diagram in which two light sources and an optical path changing unit are configured by one subunit.

FIG. 5 is a diagram showing a configuration in which the subunit shown in FIG. 4 is further provided with a cylindrical lens.

FIG. 6 is a diagram showing a configuration of a multi-channel LD array.

FIG. 7 is a schematic configuration diagram showing an example of a color image forming apparatus.

FIG. 8 is a diagram showing an example of a configuration of a laser oscillation unit.

FIG. 9 is a view showing a conventional method of supporting an entrance mirror, which is often used.

FIG. 10 is a vertical sectional view of an entrance mirror.

FIG. 11 is a side view of an array of optical elements.

FIG. 12 is a schematic configuration diagram of an optical scanning device.

[Explanation of symbols]

2 Optical scanning device 5 Optical deflector 6a, 6b Laser oscillation unit 61a, 61b LD 65 LD control board 8 rotating polygon mirror 7 Cylindrical lens P prism m1, m2 folding mirror

Continued front page    F-term (reference) 2C362 AA07 AA13 AA43 AA45 BA58                       BA71 BA82 DA08                 2H045 BA22 BA34 CB00 DA02 DA41                 5C051 AA02 CA07 DB22 DB24 DB30                       DC04 EA01 FA01                 5C072 AA03 DA02 DA04 DA10 DA21                       HA02 HA13 XA01 XA05

Claims (8)

[Claims] 1. An optical scanning device comprising a plurality of light sources and an optical deflecting device for performing optical scanning, wherein the optical deflecting device is an optical scanning device for deflecting a plurality of optical beams separated by a distance A in the sub-scanning direction. Any two of the light sources are arranged at a distance of at least a distance B larger than the distance A in the sub-scanning direction, and one or both of the light beams emitted from the two light sources are emitted. An optical scanning device comprising an optical path changing means for changing the optical path by performing reflection or refraction one or more times on the road and changing the distance between the two optical paths from the distance B to the distance A. 2. The optical scanning device according to claim 1, wherein the optical path changing unit is a parallelogram prism. 3. The optical scanning device according to claim 1, wherein the optical path changing unit is a folding mirror. 4. The optical scanning device according to claim 1, wherein the plurality of optical elements that condense the light beams emitted from the plurality of light sources in the sub-scanning direction in the vicinity of the optical deflector are provided. An optical scanning device characterized by being integrally formed. 5. The optical scanning device according to claim 1, wherein at least the two light sources and the optical path changing unit are one.
An optical scanning device provided on one subunit. 6. The optical scanning device according to claim 5, wherein the subunit includes an optical element that condenses the light beams emitted from the two light sources in the sub-scanning direction near the optical deflector. An optical scanning device characterized by the above. 7. The optical scanning device according to claim 1, wherein the optical scanning device includes one substrate for supplying signals and power to the plurality of light sources. An optical scanning device. 8. An image forming apparatus comprising a plurality of image carriers inside and comprising the optical scanning device according to claim 1. Description: