JP2011053616A - Optical scanner and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical scanner in which the advantage that the thickness in a normal line direction of a deflection means such as an oscillation mirror is small is sufficiently leveraged for reducing cost and dimensions, wherein the optical scanner contributes to making an image forming apparatus compact. <P>SOLUTION: An oscillation mirror module 400 as a deflection means includes: a movable mirror which is so arranged as to face a plane on which image carriers 101, 102, 103, 104 are arranged; a plurality of light source means 201, 202, 203, 204 which are so arranged that the main luminous fluxes of the light beams from the plurality of light source means have a predetermined angle, respectively, in a plane which is parallel to the plane on which the image carriers are arranged; an incident mirror 106 which folds back the light beams from the plurality of light source means toward the movable mirror; and a split mirror 107 which splits the plurality of light beams scanned with the movable mirror to two directions which are opposite to each other with respect to a cross section which includes the face normal line of the movable mirror and intersects with the rotary axis of the movable mirror at right angle, wherein a condensing means 205 condenses light beams so that the respective emission axes of the light source means intersect with each other on the face of the movable mirror of the deflection means. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical scanning apparatus and an image forming apparatus such as a copier, a printer, a facsimile machine, and a plotter having the optical scanning apparatus, and a multifunction machine including at least one of them.

In recent years, research on deflection devices using silicon micromachining has been promoted, and as disclosed in Patent Document 1 and Patent Document 2, a method of integrally forming a vibrating mirror and a torsion beam that pivotally supports it on a Si substrate is proposed. Has been.
Patent Documents 3 and 4 disclose examples in which a vibrating mirror is provided instead of a polygon mirror. However, according to this method, the mirror surface size can be reduced to a small size, and reciprocation can be achieved using resonance. Although it is vibrated, it has the advantages of low noise and low power consumption despite its high-speed operation. Furthermore, since the vibration is low and there is almost no heat generation, the housing for housing the optical scanning device can be thinned, and even without using a special grade resin molding material with a high glass fiber blending ratio, image quality can be improved. There is also an advantage that the influence is difficult to occur.

Patent Document 5 discloses an example in which a vibrating mirror is applied to a tandem color compatible optical scanning device. A scanning frequency fd is set according to the resonance frequency of the vibrating mirror, and a beam is set according to the set scanning frequency. It is described that by adjusting the spot interval p, it is possible to form a high-quality image without density unevenness, color shift, and color change.
Patent Document 6 discloses an example of an optical scanning device in which a separating unit is provided downstream of an optical deflector (polygon scanner). After the beam is deflected by the deflector and passes through a scanning lens, the separating unit is provided. A plurality of light beams are branched in the arrangement direction of the photosensitive drums.

  As described above, in addition to the advantages such as low noise, low power consumption, and low heat generation by using a vibrating mirror, it is a flat structure that integrally forms a vibrating mirror and a torsion beam that supports it. Compared to a polygon scanner having a predetermined dimension (inscribed circle radius) and a rotor for securing inertia, there is an advantage that the thickness of the vibrating mirror in the normal direction can be reduced.

However, conventionally, as disclosed in Patent Document 5, as in the conventional method using a polygon scanner, the rotational axis of the vibrating mirror is orthogonal to the plane on which the scanning positions of the photosensitive drums are arranged. Because of this arrangement, it is not possible to make full use of the merit that the thickness in the normal direction of the vibrating mirror is thin.
In addition, in order to make a plurality of light beams corresponding to each color obliquely enter the oscillating mirror from directions inclined at different angles in the rotation axis direction of the oscillating mirror, that is, in the sub-scanning direction, the light source unit The height of the apparatus main body is reduced by increasing the thickness of the optical scanning apparatus in the direction orthogonal to the surface on which the scanning positions of the respective photosensitive drums are arranged. It was disadvantageous.

  The present invention has been made in view of such a current situation, and can fully utilize the merit that the thickness in the normal direction of the deflecting means such as a vibrating mirror is thin, thereby realizing low cost and compactness. The main object of the present invention is to provide an optical scanning device that can contribute to downsizing of an image forming apparatus.

First, the concept of the present invention will be described below.
In order to realize a compact image forming apparatus by flatly storing the optical scanning device with respect to the arrangement surface of the plurality of photosensitive drums, it is necessary to separate the light source units so as not to interfere with each other.
Increasing the incident angle of each beam from the light source means to the cylindrical lens as the condensing means from the light source means using the cylindrical lens as the condensing means makes the light source larger. The units can be separated, and the arrangement of a plurality of light source units corresponding to the respective colors can be reduced.
By integrating the condensing means so that all of the plurality of light beams pass through, the manufacturing cost of the condensing means is reduced, the layout is improved, the assembling of the condensing means is easy, and the positioning between the light beams is performed. The error can be reduced.
Further, by using a diffractive lens having a refractive power as the light condensing means, it is possible to set a variable refraction angle for each light beam, a bending force at the same angle, and the like according to a difference in diffraction grating pattern. There are also methods for mass-producing diffraction gratings using a change in the refractive index of the exposed portion by exposing the pattern shape to a photosensitive material by vapor deposition using photolithography or holography.
Using these, the light collecting means having different refractive powers can be integrally manufactured.

  Specifically, in order to achieve the above object, the invention according to claim 1 is characterized in that a plurality of light source means modulated by image information of each color and a coupling for coupling light beams emitted from the plurality of light source means, respectively. Means, a condensing means for condensing a plurality of coupled light beams, a movable mirror rotatably supported on a pivot, and a deflecting means for collectively scanning the light beams from the light source means, and the deflection A plurality of image forming means for forming each light beam scanned by the means on an image carrier corresponding to each color, and forming a plurality of images corresponding to each color. In an optical scanning device used in an image forming apparatus in which corresponding image carriers are arranged in the same plane, the deflecting unit is arranged so that the movable mirror faces the plane in which the image carriers are arranged. And The plurality of light source means are arranged so that the main luminous fluxes of the light beams from the plurality of light source means each have a predetermined angle in a plane parallel to the plane, and the light beams from the plurality of light source means are movable. An incident mirror that turns back to a mirror and a plurality of light beams scanned by the movable mirror are split in two directions that are opposite to the cross section that includes the surface normal of the movable mirror and is orthogonal to the rotational axis of the movable mirror A mirror, and the condensing means condenses so that each emission axis of the light source means intersects with a movable mirror surface of the deflecting means, and scans the image carrier corresponding to each color. It is characterized by becoming.

According to a second aspect of the present invention, in the optical scanning device according to the first aspect, the condensing unit bends at least one light beam in a direction in which any one set of the plurality of adjacent light beams is separated. It is characterized by.
According to a third aspect of the present invention, in the optical scanning device according to the first or second aspect, the condensing means is integrally formed so that all of the plurality of light beams pass therethrough.
According to a fourth aspect of the present invention, in the optical scanning device according to any one of the first to third aspects, all of the plurality of light beams are bent at the same angle.

According to a fifth aspect of the present invention, in the optical scanning device according to any one of the first to third aspects, a pair of adjacent light beams corresponding to a pair of the condensing means is bent at the same angle. It is characterized by that.
According to a sixth aspect of the present invention, in the optical scanning device according to any one of the first to third aspects, a diffractive lens is used as the condensing unit.
A seventh aspect of the present invention is the optical scanning device according to any one of the first to sixth aspects, further comprising a support member that integrally supports a plurality of light source means corresponding to each color, and the support member The light collecting means has a positioning portion for determining the positional relationship, and the support member and the light collecting means are integrally fixed.
According to an eighth aspect of the present invention, an image forming apparatus includes the optical scanning device according to any one of the first to seventh aspects.

According to the present invention, the advantage that the thickness in the normal direction of the deflecting means such as a vibrating mirror is thin can be fully utilized, thereby realizing low cost and downsizing, and miniaturization of the image forming apparatus. Can contribute.
According to the present invention, the condensing means is integrally formed so that all of the plurality of light beams pass, thereby reducing the cost by reducing the number of parts and simplifying the mounting process. In addition, the positional relationship with each light beam can be matched with high accuracy. In addition, when installing individually, a positioning member and a fixing member are needed for each, and the processing precision error of an individual component accumulates, and positioning adjustment becomes complicated.
Since the plurality of light source means corresponding to each color is integrally supported by the support member, it can be incorporated in the housing while maintaining the arrangement accuracy between the plurality of light source means corresponding to each color. Productivity is improved and a low-cost optical scanning device can be realized.

According to the present invention, a plurality of light beams bend at the same angle, thereby bending at the same angle θa (angle between the incident axis from the light source and the exit axis from the cylindrical lens to the reflecting mirror) as shown in FIG. Therefore, the layout of the optical system from the light source can be shared with the optical element from the reflecting surface of the deflecting means, the design period can be shortened, and the cost of parts such as the optical element can be reduced. The deviation of the optical characteristics can be finely adjusted, and a more stable image can be formed.
According to the present invention, a plurality of light beams are appropriately arranged by a surface having a bending force of the light collecting means by bending one set of light beams corresponding to a pair of adjacent light collecting means at the same position angle. And can be appropriately disposed at a desired position with respect to the optical element. In addition, if the oblique incidence angle can be set between pairs of the same angle, the design layout and parts can be shared, the design period can be shortened and the parts can be manufactured, and the angle of each optical element can be reduced. The labor for adjustment can be saved, the productivity can be improved, and a low-cost optical scanning device can be realized.

  According to the present invention, a diffraction grating having a bending force is formed on the surface of the condensing unit by using a diffractive lens for the condensing unit. It becomes easy to arrange the light source means by bending and separating the light beams. A plurality of light beams can be appropriately separated by forming the diffraction grating pattern in accordance with the separation angle for each light beam. Further, by manufacturing the diffraction grating by a photolithography technique or the like, it is possible to facilitate the thinning and mass production of the light collecting means.

According to the present invention, there is provided a support member that integrally supports each light source means, and a positioning portion with the support member is provided in the light condensing means, and these are fixed integrally, thereby In the housing, the light source means and the light collecting means can be laid out at appropriate positions, and the relative arrangement of the reflection mirrors of the light source means and the deflecting means and the ridgeline where the reflection surfaces of the separation mirror intersect can be reliably positioned. Then, after branching by the separation mirror, the scanning trajectory on each surface to be scanned can be kept parallel, the accuracy of overlaying the color plates can be improved, and high-quality image formation can be performed.
In addition, according to the present invention, it is possible to realize a low-cost and compact image forming apparatus.

1 is a schematic perspective view of an optical scanning device according to an embodiment of the present invention. It is a perspective view of a light source module. It is a perspective view of a vibration mirror module. It is a disassembled perspective view which shows the support structure to the housing of a vibration mirror module. It is a perspective view which shows the relationship between an incident mirror, a movable mirror, and a separation mirror. 1 is a schematic configuration diagram of an image forming apparatus. It is a perspective view for demonstrating a function when there is no separation effect by refractive power in a condensing means. It is a top view which shows the example in case all the some light beams bend at the same angle. It is a figure for demonstrating the magnification shift prevention function. It is a figure which shows the correction | amendment of the bending residual of a scanning locus | trajectory. It is a figure which shows the deflection angle change of a movable mirror. It is a perspective view which shows another Example of a light source module. It is a schematic diagram of the diffraction lens for bending the light beam which passes a condensing means. It is a figure which shows the external appearance of a multi-beam semiconductor laser. It is a schematic diagram which shows the inclination state in the case of mounting | wearing inclining by making the injection axis of a multi-beam semiconductor laser into a rotating shaft.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows the configuration of an optical scanning device that scans four stations with a single vibrating mirror. FIG. 3 shows a configuration of a vibrating mirror module 400 as a deflecting unit. In the present embodiment, an example is shown in which a vibrating mirror that generates rotational torque by a piezoelectric drive system is used as the deflecting means.
In addition to piezoelectric driving, electromagnetic driving and electrostatic driving are known as methods for generating rotational torque, but both methods are the same.
The oscillating mirror module 400 includes a movable mirror 401 that forms a mirror surface on its surface and forms a vibrator, a torsion beam 402 that supports the movable mirror 401, a cantilever 403 that generates rotational torque on the torsion beam, and a support portion thereof. An Si frame is cut out by etching.

The width of the torsion beam 402 is 40 to 60 μm, the cantilever 403 is formed symmetrically with the rotation axis in between, the four corners of the torsion beam are connected to the frame 404, and the PZT film 405 is formed on the surface.
The PZT film 405 expands and contracts by alternately applying positive and negative voltages, the cantilever 403 is bent to generate a rotational torque, and the torsion beam 402 is twisted to reciprocate the movable mirror 401.
When this voltage switching period is made close to the natural frequency of the primary vibration mode with the torsion beam of the vibrator as the rotation axis, so-called resonance frequency f0, the amplitude is excited and a large deflection angle can be obtained.
In this embodiment, the deflection angle is ± 25 °, and the incident light beam is scanned at a maximum of ± 50 °.
Normally, the scanning frequency fd is set or controlled so as to follow the resonance frequency f0. However, the resonance frequency f0 is determined by the moment of inertia I of the oscillating movable mirror. If there is a variation in the finished dimensional accuracy cut out by etching such as the width of each, a difference occurs between individuals, and it is difficult to align the scanning frequencies fd of the individual vibrating mirror modules.

Here, the resonance frequency f0 is a characteristic value unique to the vibration mirror module, and is described separately from the scanning frequency fd that can be set or selected in a stepwise manner by the mirror drive circuit by clock division.
The variation of the resonance frequency f0 depends on the capability of the etching process, but occurs at about ± 100 Hz. For example, if the target scanning frequency fd = 2 kHz, 0. When a 5% scan pitch shift occurs, this scan pitch shift accumulates at the end of the image, resulting in a change in image width (magnification shift) in the sub-scan direction by several mm (for example, 1.5 mm).
For this reason, in the present embodiment, as shown in FIG. 9, in a writing control circuit described later, image data is inserted and thinned between lines in accordance with the resonance frequency f0 of the vibration mirror module 400 incorporated in the apparatus. This prevents the magnification deviation from occurring.

The operation will be described below.
In FIG. 9, for the purpose of explanation, the number of main scanning dots corresponding to one line is assumed to be 10 dots.
For example, assuming that there is a shift in the scanning frequency fd corresponding to one line in 12 lines, in other words, a magnification shift of 8%, the magnification shift η and the number of main scanning dots Nm are Ns = 1 / η = 1/0. 08 = 12
k = Nm / (Ns / 2-1) = 10 dots / 5 = 2 dots
In other words, the shift in magnification can be corrected by shifting the target pixel to the adjacent line while increasing the number of pixels for every other line by 2 dots.
As described above, when the resonance frequency f0 is high, that is, when it is desired to increase the magnification, the pixel data is shifted to the adjacent line later, and conversely, when the resonance frequency f0 is low, that is, when the magnification is to be reduced. Converts the developed original image data so as to thin out adjacent pixels to be shifted by shifting the pixel data to the previously adjacent line.

Normally, the number of main scanning dots Nm is 600 dpi, and the A4 width is 4960 dots, so if you want to shift the 5% magnification,
Ns = 1 / η = 1 / 0.05 = 20
k = Nm / (Ns / 2-1) = 4960 dots / 9 = 551 dots
If you want to shift the 0.5% magnification,
Ns = 1 / η = 1 / 0.005 = 200
k = Nm / (Ns / 2-1) = 4960 dots / 99 = 50 dots
This can be dealt with by increasing the number of target pixels to be shifted once as the magnification deviation increases.

On the other hand, as shown in FIG. 10, pixel data is shifted to a positional relationship that reverses the bending residual as shown in FIG. Thus, the image can be made inconspicuous as well.
In the write control circuit, these are ANDed to convert the original image data and stored in the frame memory, read out as raster data in units of one line, and transferred to the light source drive circuit using the synchronization detection signal as a trigger. The light source driving circuit modulates the semiconductor laser based on the raster data.
In this embodiment, it has a synchronous detection sensor 117 and a termination detection sensor 118 so that the amplitude of the vibrating mirror module can be detected. In the mirror drive circuit, when starting up, based on these detection signals, The scanning frequency fd is swept stepwise, the scanning frequency fd closest to the resonance frequency f0 having the maximum amplitude is detected, and the scanning frequency fd is set.
Further, in the writing control circuit, the insertion of image data and the number of thinned pixels are determined based on these detection signals in accordance with the deviation from the center value of the set scanning frequency fd so that the magnification deviation is minimized. .
In the light source driving circuit, the reference clock fh for modulating the light source is determined according to the set scanning frequency fd so that the ratio between the reference clock fh and (scanning frequency fd / number of light source channels) is constant. fh is varied.

  As shown in FIG. 1, an optical scanning device 300 that scans each photosensitive drum is integrally configured to display yellow, magenta, cyan, and black images arranged at equal intervals along the moving direction 105 of the transfer body. With respect to the four photosensitive drums 101, 102, 103, and 104 to be formed, a plurality of light beams from light sources corresponding to the respective photosensitive drums 101, 102, 103, and 104 are applied to a plane parallel to the rotation axis including the surface normal of the movable mirror in the vibration mirror module The light beam from each light source is incident on the surface of the movable mirror at a different angle with respect to the surface normal within a cross section inclined at a predetermined angle about the rotation axis of the movable mirror, and is deflected to each photosensitive drum after deflection. As a result, image recording is simultaneously performed at a plurality of image forming stations.

The scanning positions on the photosensitive drum surface corresponding to the respective colors are arranged so as to be on the same plane, and the rotation axis of the movable mirror is arranged in parallel to the same surface and orthogonal to the photosensitive drum axis.
The scanning position is arranged on the emission axis from the light source module composed of the semiconductor lasers 201, 202, 203, 204 as the light source means corresponding thereto and the coupling lenses 205, 206, 207, 208 as the coupling means. In a plane parallel to the surface to be moved, they are arranged at a predetermined angle so as to be incident at different angles in the direction of the movable mirror rotation axis.

FIG. 2 is a perspective view of the light source module 200.
As shown in FIG. 2, the semiconductor lasers 201, 202, 203, and 204 of the respective colors are radially arranged on the resin support member 213 so that the emission axes intersect at substantially the same point, and maintain the relative positions. It is supported integrally.
The support member 213 has a symmetrical shape with respect to the cross section that includes the surface normal of the movable mirror 401 and is orthogonal to the rotation axis, so that the arrangement direction of 2ch beam spots on each photosensitive drum surface is aligned at each station. .
Each semiconductor laser press-fits the cylindrical outer periphery of the CAN package into a fitting hole (not shown) formed along the emission axis from the back surface of the support member 213, and the coupling lenses 205, 206, 207, 208 corresponding to each are The protrusion 215 having a U-shaped mounting surface protruding from the support member 213 is filled and fixed with an adhesive in the gap with the edge.
A light source driving circuit for a semiconductor laser is formed on the printed circuit board 216, and is shared by a plurality of semiconductor lasers. The printed circuit board 216 is screwed to a support 217 formed on a support member 213, and each lead terminal is soldered to be connected to the circuit. The
In this embodiment, since each of the semiconductor lasers corresponding to each color is 1ch, a light source drive circuit for 4ch is formed.

In order to support high-speed writing, a plurality of lines can be simultaneously written with a multi-channel semiconductor laser of 2ch or more. For example, if each multi-beam semiconductor is 2ch, a light source drive circuit for 8ch is formed.
The light source module 200 engages the projection 220 protruding from the bottom surface with the square hole 10 of the housing to position the arrangement center position of the semiconductor laser, and is fixed to the seat surface provided in the housing at the fixing hole portions 219 at both ends. .
The contact surface of the fixed hole 219 with the housing seat surface is formed perpendicular to the surface on which the emission axes of the multi-beam semiconductor lasers are arranged, and is supported perpendicular to the rotation axis of the movable mirror 401.

Light beams from the respective semiconductor lasers 201, 202, 203, and 204 are converged in the same direction through a cylindrical lens 216, which is a condensing unit having a refractive power in the rotation axis direction of the movable mirror 401, and on the surface of the movable mirror 401. It is imaged linearly.
In the present embodiment, the lens portions through which the light beams from the multi-beam semiconductor lasers 201, 202, 203, and 204 pass are integrally formed of resin. A cylindrical surface is formed on the second surface, and the first surface is not parallel to the surface orthogonal to the emission axis, so that the incident light beam is bent in the array plane of the emission axis, and each multi-beam semiconductor laser The light beams from 201 and 202, 203 and 204 are emitted from the cylindrical lens 216 at an angle θ2 smaller than the angle θ1 formed by the light beam reaching the cylindrical lens 216.
Thereby, the incident angle difference between the multi-beam semiconductor lasers in the direction of the rotation axis to the movable mirror 401 can be made more acute, and the optical path length from the movable mirror as the deflecting means to the semiconductor laser as the light source means can be increased as compared with the prior art. The light beam can be bent and sufficiently separated from each other, and each semiconductor laser and coupling lens can be arranged.
Further, it is possible to reduce the deterioration of the beam spot due to the bending of the scanning locus and the optical aberration accompanying the oblique incidence.

In addition, by forming a cylindrical surface on the first surface of the cylindrical lens and making the second surface non-parallel to the surface orthogonal to the exit axis, the incident light beam is bent more greatly within the array plane of the exit axis. Can be made.
When the light beam is bent by the collimator lens 205, the first surface is not parallel to the surface orthogonal to the emission axis, and the collimated surface is formed on the second surface so that the light beam is bent and separated. can do.

  A positioning portion that determines the positional relationship with the support member 213 may be formed in the cylindrical lens 216 as a light collecting unit, and the support member 213 and the cylindrical lens 216 may be fixed integrally.

FIG. 13 shows a schematic diagram of a diffractive lens for bending the light beam passing through the light condensing means.
In the figure, assuming that the refractive index is n, the apex angle is δ, the grating length Λ, and the deflection angle ε (angle formed by the incident light beam and the outgoing light beam), the following relational expression is established based on a small angle approximation.
ε = (n−1) · δ
By forming the shape of the diffraction grating in accordance with a desired bending angle, each of the plurality of light beams can be appropriately separated.
By forming a diffraction grating on the surface by photolithography technology, a type that gives a path difference by unevenness, a type that gives a path difference by a difference in refractive index, and a type that gives a constant path difference (phase difference) in a sawtooth cross section ( A prism diffraction grating) is often used.

As shown in FIG. 7, the surface through which the light beam passes on the inner side and the outer side is the same plane so that the first surface of the cylindrical lens 216, which is a case where the condensing means has no separation effect due to refractive power, is indicated by a dotted line. In such a case, the light beams at both ends in the sub-scanning direction cannot be separated as indicated by the alternate long and short dash line, and the collimating lens and the semiconductor laser constituting the light source means cannot be arranged in an appropriate layout.
Further, in order to sufficiently separate the light source means, it is necessary to dispose the light source means at a position away from the deflecting means, which leads to an increase in the size of the apparatus and the semiconductor laser forms an image on the image carrier via the writing optical system. The light intensity becomes weak as the optical path length increases, and it becomes difficult to form a sharp latent image.
In addition, widening the incident angle difference between the semiconductor lasers to ensure a sufficient separation for arranging the plurality of semiconductor lasers, as a detrimental effect due to the difference in the oblique incident angle between the plurality of light beams, Deterioration of the beam spot shape due to aberration, which is an optical characteristic, and the difference in characteristics among multiple light beams becomes significant. The latent image formed on the image carrier is different at each station, and color misregistration is formed. It will cause image deterioration.

FIG. 8 shows an embodiment in which all of a plurality of light beams are bent at the same angle.
Since it bends at the same angle θa (angle formed by the exit axis and the incident axis of each light beam from the cylindrical lens), the coupling lens and the cylindrical lens, their fixing jig, and the light source means at a plurality of stations The fixing means can be shared, and the manufacturing cost and assembly cost can be reduced.
In addition, since the imaging element can be used in common, the design period can be shortened, and variations in the optical characteristics of the beam spot due to differences in the surface shape of the optical element between stations can occur. And a more uniform beam spot.
Moreover, even if all angles cannot be made the same, by making the angle at which the adjacent pair of corresponding light beams bend the same angle, the optical element can be shared, and the design period can be shortened. Cost reduction by sharing parts and adjustment of characteristics between the light beams can be simplified.

As shown in FIG. 5, the plurality of light beams emitted from the cylindrical lens 216 have the surface normal of the movable mirror 401 around the rotation axis by the incident mirror 106 having a reflection surface parallel to the rotation axis of the movable mirror 401. The light enters the movable mirror 401 so as to be aligned in a plane including an axis inclined at a predetermined angle.
At this time, light beams from the respective semiconductor lasers 201, 202, 203, and 204 are symmetric with respect to a cross section that includes the surface normal of the movable mirror 401 and is orthogonal to the rotation axis, on the surface of the movable mirror in the direction of convergence. After being incident and intersecting at the movable mirror surface, it is reflected in discrete directions.
The light beam reflected by the surface of the movable mirror 401 is a separation mirror 107 having a pair of reflecting surfaces, which are provided immediately after, and have a cross section perpendicular to the rotation axis as a ridge line and are inclined in a predetermined angle from the same surface. Therefore, the light beams from the multi-beam semiconductor lasers 201 and 202 and 203 and 204 are reflected so as to be branched in two opposite directions.

FIG. 4 shows a support portion of the oscillating mirror module 400 to a housing (not shown).
The oscillating mirror module 400 has a configuration in which the movable mirror portion formed of the Si substrate described above is mounted in a ceramic package 407 having lead terminals, and the interior is decompressed and sealed by a glass window 408. The mirror 401 is mounted with its surface facing downward.
The ceramic package 407 is provided with a pair of protrusions 409 arranged on the extension line of the rotation axis of the movable mirror 401, and the package surface is mounted on the mounting surface 411 inclined at a predetermined angle with respect to the bottom surface of the support member 410 formed in a U shape. , The projection 409 is engaged with the groove 412, and positioning in the direction of the rotation axis with the surface normal of the movable mirror 401 as an axis is performed, whereby the incident mirror 106, the separation mirror 107, and a scanning lens described later Positioning of the optical axes 108 and 109 and the amplitude center of the movable mirror 401 is performed.
In the present embodiment, the scanning lenses 108 and 109 are formed on the side surface of the support member 410 by engaging and positioning the grooves 414 provided in the flat pressing portions at both ends with the convex portions 415 and joined together. .

The support member 410 to which the vibration mirror module 400 and the scanning lenses 108 and 109 are assembled has four protruding portions 416 protruding from the bottom surface fitted in the square holes of the housing, and the incident mirror 106, the separation mirror 107, and the light source module. It is attached to the housing in accordance with the arrangement of 200.
In addition, the incident mirror 106 and the separation mirror 107 are integrally formed of a resin, and a bottom surface formed in parallel with a surface on which the emission axes of the multi-beam semiconductor lasers are arranged comes into contact with the housing seat surface. The pair of positioning pins 413 protruding from the housing are fitted into the round holes of the housing, and the positioning on the housing seat surface is performed so that the ridgeline of the separation mirror 107 and the cross section F perpendicular to the rotation axis of the movable mirror 401 are aligned. Will be installed.
With the above configuration, the relative arrangement of the light source module 200, the incident mirror 106, the separation mirror 107, the movable mirror 401, and the scanning lenses 108 and 109 can be accurately positioned and mounted on the housing.

FIG. 11 shows an outline of the change in the swing angle of the movable mirror over time.
Since the movable mirror 401 is resonantly oscillated, the deflection angle θ changes in a sin wave shape with time t. Therefore, when the maximum deflection angle of the movable mirror, that is, the amplitude is θ0 and the scanning frequency fd,
θ = θ0 · sin2πfd · t
Therefore, the scanning lenses 108 and 109 are designed so that the moving speed of the beam spot on the surface of the photosensitive drum is constant with respect to the change dθ / dt of the deflection angle.
The light beam from the semiconductor laser 201 is branched by the separation mirror 107, passes through the scanning lens 108, and records a black image on the photosensitive drum 101 via the folding mirror 110.
The light beam from the semiconductor laser 202 is branched by the separation mirror 107, passes through the scanning lens 108, and records a cyan image on the photosensitive drum 102, which is an image carrier, via the folding mirrors 111 and 112.
Similarly, the stations that are symmetric with respect to the plane orthogonal to the rotation axis of the movable mirror 401 are branched by the separation mirror 107 in a direction opposite to the above stations, and then pass through the scanning lens 109 to be respectively photoreceptor drums 104, A yellow image and a magenta image are recorded in 103.

The synchronization detection sensor 117 and the end detection sensor 118 detect a light beam from the multi-beam semiconductor laser 204 that forms a yellow image outside the scanning region, generate a synchronization detection signal that matches the timing of writing in each station, and are movable. The amplitude of the mirror 401 and the phase and offset of the amplitude are detected.
In this embodiment, the amplitude θ0 = 25 °, the detection scanning angle θs = 18 ° of the synchronization detection sensor and the end detection sensor, and the scanning angle θd = 15 ° corresponding to the image area (LGATE), and the detection signal of each sensor is Based on this, the amplitude is controlled by measuring the times t1, t2, and t3.
For example, if there is a deviation of the amplitude θ0, the scanning speed on the surface of the photosensitive drum will change and the image width in the main scanning direction will change, and if there is a phase deviation or offset deviation, the writing position deviation or scanning will occur. A local change in magnification occurs in the direction, causing color misregistration and density unevenness.

If a beam corresponding to a scanning angle of 2θs is detected in each sensor, detection signals are generated in backward scanning and forward scanning. In the case of a synchronous detection sensor, using the time difference t1,
θs = θ0 · cos2πfd · t1 / 2
Since θs is fixed, it can be seen that the amplitude θ0 can be detected by measuring t1.
Similarly, by detecting t2 and t3 with the end detection sensor, a phase shift in the time axis direction and an offset shift in the amplitude center can be detected.
Therefore, by adjusting the gain applied to the oscillating mirror module 400 and the timing of the reference clock, the deviation from the initial value can be corrected to always maintain a stable amplitude.

FIG. 6 shows an example of an image forming apparatus equipped with an optical scanning device.
Around the photosensitive drum 301, a charging charger 302 that charges the photosensitive member to a high voltage, a developing roller 303 that attaches a charged toner to an electrostatic latent image recorded by the optical scanning device 300, and visualizes it, a developing roller A toner cartridge 304 for replenishing toner and a cleaning case 305 for scraping and storing toner remaining on the drum are arranged. Each image forming station basically has the same configuration except that the toner color is different.
The movable mirror 401 is driven at a predetermined scanning frequency, and the light source is modulated by the image data of each color read in accordance with the image writing timing, and image recording is performed line by line in one cycle of the movable mirror 401. .
The yellow, magenta, cyan, and black image forming stations are arranged in parallel in the moving direction of the transfer belt 306, and the toner images formed on the photosensitive drums are sequentially transferred onto the transfer belt at the same timing (primary transfer). Then, they are superimposed on the transfer belt to form a toner image in which yellow, magenta, cyan, and black are mixed.
The toner images superimposed on the transfer belt are transferred (secondary transfer) to the recording paper fed out from the paper feed tray 307 at the appropriate timing.
The recording paper on which the toner image has been transferred is fixed by the fixing device 310 and discharged to the paper discharge tray 311 by the paper discharge roller pair 312.

FIG. 12 shows another embodiment of the light source module.
This is an example in which a multi-beam semiconductor laser is used as a semiconductor laser as a light source.
An appearance of a multi-beam semiconductor laser 501 as a light source is shown in FIG.
A light source chip 510 (not shown) is mounted on the lead frame with a joint surface parallel to the active layer, and is covered with a resin cover 511. In the embodiment, a plurality of (2ch) light sources are monolithically formed and arranged in a plane parallel to the lead frame 509. The light beam from each light source is emitted in parallel with the lead frame 209. Note that the multi-beam semiconductor laser of 2ch or more has the same configuration except that the lead terminals are increased by the number of light sources.
The lead terminal 512 extends to the lead frame 509 and is connected to each of a plurality of light emitting sources by wire bonding and can be driven independently.

As shown in FIG. 12, the light source module integrally supports multi-beam semiconductor lasers 501, 502, 503, and 504 for each color.
The multi-beam semiconductor laser 501 has a lower surface of the lead frame 509 in contact with a mounting surface 514 formed on a resin support member 513 and is fitted between protrusions 518 erected so as to sandwich the lead frame 509. Are positioned and fixed, and maintain the relative arrangement of the plurality of light emitting sources.
By the way, the overall magnification in the sub-scanning direction of the imaging optical system constituting the optical scanning device is 1.5 to 2 times, and the pitch in the sub-scanning direction between adjacent beam spots by the light beams from a plurality of light sources is set. If the scanning pitch corresponding to 600 dpi is adjusted to 42.4 μm, the arrangement angle γ is approximately γ = sin −1 (42.4 / 1.5 to 2/50) = 34.4 ° ~ 25.1 °
It becomes. That is, in order to obtain a predetermined scanning line pitch on the surface of the photosensitive drum, as shown in FIG. 15, it is necessary to mount the multi-beam semiconductor laser 501 with the emission axis as a rotation axis, and the mounting surface 514 is attached. It is tilted in advance.

As shown in FIG. 12, the coupling lens 505 is bonded and fixed to the mounting surface 515 by filling the gap with the edge portion with an adhesive, and the mounting surface 515 is formed to be inclined in the same manner as the mounting surface 514.
Further, the support member 213 has a symmetric shape with respect to a cross section that includes the surface normal of the movable mirror 401 and is orthogonal to the rotation axis, and the direction in which the multi-beam semiconductor laser 501 is inclined is symmetric. The arrangement direction of the 2ch beam spots in FIG.
The multi-beam semiconductor lasers are arranged radially so that the emission axes intersect at substantially the same point, and are supported integrally with the support member 513 while maintaining a relative position.
A light source driving circuit for a multi-beam semiconductor laser is formed on the printed circuit board 516, and is shared by a plurality of multi-beam semiconductor lasers. The printed circuit board 516 is screwed to a support column 517 formed on a support member 513, and each lead terminal 512 is soldered. Circuit connection. In the embodiment, since each multi-beam semiconductor laser corresponding to each color is 2ch, a light source driving circuit for 8ch is formed.

The light source module 500 engages the projection 520 protruding from the bottom surface with the square hole of the housing to position the center position of the arrangement of the multi-beam semiconductor lasers, and is fixed to the seat surface provided on the housing at the flange portions 519 at both ends. .
The contact surface of the flange portion 519 with the housing seat surface is formed in parallel with the surface on which the emission axes of the multi-beam semiconductor lasers are arranged, and is supported in parallel with the rotation axis of the movable mirror 401.
The light beams from the multi-beam semiconductor lasers 501, 502, 503, and 504 are converged in the same direction through a cylindrical lens 516 having refractive power in the rotation axis direction of the movable mirror 401, and are linearly formed on the surface of the movable mirror 401. Imaged.

In the embodiment, the lens portions through which the light beams from the multi-beam semiconductor lasers 501, 502, 503, and 504 pass are integrally formed of resin. A cylindrical surface is formed on the second surface, and the first surface is not parallel to the surface orthogonal to the emission axis, so that the incident light beam is bent in the array plane of the emission axis, and each multi-beam semiconductor laser The light beams from 501 and 502 and 503 and 504 are emitted from the cylindrical lens 516 at an angle θ2 smaller than the angle θ1 formed by the light beam reaching the cylindrical lens 516.
This makes it possible to make the incident angle difference between the multi-beam semiconductor lasers in the rotation axis direction to the movable mirror 401 more acute, and to reduce the deterioration of the beam spot due to the bending of the scanning locus and the optical aberration due to the oblique incidence. The multi-beam semiconductor lasers 501, 502, 503, and 504 of each color are radially arranged on the resin support member 513 so that the emission axes intersect at substantially the same point, and are supported integrally while maintaining their relative positions. Has been.

101, 102, 103, 104, 301 Photosensitive drum as image carrier 106 Incident mirror 107 Separating mirror 108, 109 Scanning lens 201, 202, 203, 204 as imaging means Semiconductor laser 205 as light source means Coupling means Coupling lens 216 Condensing means 401 Movable mirror 400 Vibrating mirror module as deflecting means

Japanese Patent No. 2924200 Japanese Patent No. 30111144 Japanese Patent No. 3445691 Japanese Patent No. 3543473 JP 2007-233235 A JP 2001-281575 A

Claims (8)

A plurality of light source means modulated by image information of each color;
Coupling means for coupling each of light beams emitted from the plurality of light source means;
Condensing means for condensing a plurality of coupled light beams;
A deflecting unit that has a movable mirror rotatably supported by the shaft and collectively scans the light beam from the light source unit;
A plurality of imaging means for imaging each light beam scanned by the deflection means on an image carrier corresponding to each color;
An optical scanning apparatus that forms a plurality of images corresponding to each color, and is used in an image forming apparatus in which image carriers corresponding to the respective colors are arranged in the same plane.
The deflecting means is arranged so that the movable mirror faces a plane on which the image carrier is arranged,
The plurality of light source means are arranged such that main luminous fluxes of light beams from the plurality of light source means each have a predetermined angle in a plane parallel to the plane,
An incident mirror that turns back the light beam from the plurality of light source means to the movable mirror;
A separation mirror that branches a plurality of light beams scanned by the movable mirror in two directions opposite to a cross section that includes a surface normal of the movable mirror and is orthogonal to the rotation axis of the movable mirror;
The condensing means condenses light so that the emission axes of the light source means intersect at the movable mirror surface of the deflecting means, and scans the image carrier corresponding to each color. Optical scanning device. The optical scanning device according to claim 1,
The light condensing unit bends at least one light beam in a direction in which any one of the adjacent sets of the plurality of light beams is separated. The optical scanning device according to claim 1 or 2,
The optical scanning device characterized in that the condensing means is integrally formed so that all of the plurality of light beams pass therethrough. In the optical scanning device according to any one of claims 1 to 3,
An optical scanning device characterized in that all of the plurality of light beams are bent at the same angle. In the optical scanning device according to any one of claims 1 to 3,
An optical scanning device characterized in that a pair of light beams corresponding to a pair of adjacent condensing means is bent at the same angle. In the optical scanning device according to any one of claims 1 to 3,
An optical scanning device using a diffractive lens for the condensing means. In the optical scanning device according to any one of claims 1 to 6,
A support member that integrally supports a plurality of light source means corresponding to each color; and a positioning portion that determines a positional relationship with the support member is provided in the light collecting means, and the support member, the light collecting means, An optical scanning device characterized by fixing the two integrally.   An image forming apparatus comprising the optical scanning device according to claim 1.

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