JP2003262819A - Optical scanner and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive optical scanner and an image forming apparatus capable of realizing an image where jitter or color slurring is hardly found without making the flatness of a polygon mirror more accurate. <P>SOLUTION: In the optical scanner, a laser beam radiated from a light source is deflected to perform scanning by the polygon mirror, and condensed toward a surface to be scanned by a scanning image-formation optical system and further a laser beam transmission member is provided in the optical path of the scanning image-formation optical system. The flatness shape of the reflection surface of the polygon mirror is nearly the same on each surface. <P>COPYRIGHT: (C)2003,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 and an image forming apparatus, and more particularly to an optical scanning device having a polygon mirror.

[0002]

2. Description of the Related Art Conventionally, a polygon scanner used in a color image forming apparatus or the like has a method in which a plurality of laser beams are made incident and deflected, and a method of arranging two mirrors at an axial interval is performed. ing. On the other hand, in order to realize high-speed printing and high image quality of the color image forming apparatus, it is necessary to rotate the polygon scanner at a high speed of 30,000 rpm or higher and with high accuracy. In the color image forming apparatus, laser beams for each color (yellow, magenta, cyan, black) are scanned,
The scanning jitter of the polygon scanner produces "vertical line fluctuation" and "color shift" images. Therefore, in high image quality,
There is a demand for reducing the jitter of the polygon scanner, and for that purpose, it is necessary to reduce the variation in the flatness of each polygon mirror.

A pixel density of 1200 dpi or more is required for high image quality. Therefore, the spot diameter (1 / e ² , the same applies hereinafter) of the laser beam on the surface of the photosensitive member must be reduced to 50 μm or less. It is said that. However, in order to stably maintain a small-diameter laser beam, the flatness of the polygon mirror has a large influence, and it is necessary to improve the accuracy. For example, unless the flatness is set to 0.1 μm or less, the beam spot diameter in the main scanning direction is greatly different between the both ends and the central portion, and the image is disturbed especially when both ends of the thin line are thickened.

In order to solve such problems, the precision of the polygon mirror flatness is improved (reduction of the flatness within one surface and variation of each surface), the improvement of the polygon mirror processing accuracy, the polygon mirror flatness. It is necessary to maintain the high precision of each. Requires higher precision of the mirror finishing machine, while the conventional processing method also increases the number of processing steps and lowers the yield, resulting in higher costs. When fixing the polygon mirror from above, deformation occurs due to leaf springs and screws. There is a fear. As a preventive measure, it is conceivable to reduce the fixing force or fix with an adhesive, but in both cases, the polygon mirror slightly moves, the balance of the rotating body is likely to change, and this causes vibration. 30000 rpm used especially for color image forming devices
In the case of the above-described two-stage polygon mirror rotating at a high speed, the polygon mirror is exposed to 90 ° C. or higher due to windage and heat generation of the motor. Parts that make up the rotating body (polygon mirror,
Even if the coefficient of thermal expansion of the flange and shaft on which the rotor magnet is fixed are different or even if they match, strict control and inspection of component tolerances and fixing methods will cause slight movement during high-temperature high-speed rotation (balance change of the rotating body). Occurs, which in turn results in increased vibration.

Therefore, according to Japanese Patent Laid-Open No. 2000-28953 (hereinafter referred to as a conventional example), the polygon mirror is pressed against the flange portion of the rotary sleeve fitted to the fixed shaft by the disk member, the corrugated plate and the stopper, and is integrated. Are combined together. In order to improve the jitter by increasing the moment of inertia of the rotating body including the rotor magnet, which is integrated with the rotating sleeve, and the polygon mirror, etc., a disk member with a diameter larger than that of the polygon mirror is added, and the balance correction groove is on the upper surface. Is provided. Further, the polygon mirror is covered with a housing supporting the fixed shaft and a disk member to form a dust-proof cover. With this configuration, it is possible to prevent the rotation jitter of the small-diameter polygon mirror from being deteriorated in an overfield type scanning system or the like.

[0006]

However, by adding a disk member having a diameter larger than that of the polygon mirror as in the above-mentioned conventional example, the start time is extended by increasing the inertia, and the bearing load is increased by increasing the mass. Causes an increase in power consumption. Further, since the disc member is mounted on the upper end portion of the rotating body, the center of gravity of the rotating body is displaced to the upper end portion, causing many problems such as destabilizing the balance of the rotating body.

The present invention is intended to solve these problems, and an inexpensive optical scanning device and image forming capable of realizing an image with less jitter and color misregistration without increasing the precision of the polygon mirror flatness. The purpose is to provide a device.

[0008]

In order to solve the above-mentioned problems, an optical scanning in which a laser beam emitted from a light source is deflected and scanned by a polygon mirror, and a scanning and imaging optical system focuses the laser beam toward a surface to be scanned. The device is characterized in that a laser beam transmitting member is provided between the optical paths of the scanning and imaging optical system. Therefore, an image with less jitter and color misregistration can be realized without increasing the precision of the polygon mirror flatness.

Further, since the flatness shape of the reflecting surface of the polygon mirror is substantially the same for all the surfaces, the laser beam position shift in the main scanning direction can be reduced without increasing the accuracy of the polygon mirror flatness. This makes it possible to realize images with less jitter and color misregistration.

Further, it is preferable that the flatness of the reflecting surface of the polygon mirror is substantially concave or convex.

Further, it is preferable that the flatness shape of the laser beam transmitting member in the main scanning direction is substantially concave or convex.

Further, since the flatness of each flatness shape of the polygon mirror and the laser beam transmitting member is within the effective range corresponding to the scanned surface area, the precision of the reflecting surface of the polygon mirror is increased more than necessary. You do n’t need
An inexpensive optical scanning device can be provided.

Further, when the powers of the laser beam transmitting member and the polygon mirror in the main scanning direction are P1 and P2, respectively, | P1−P2 | <4 × 10 ⁻⁶ [1 / mm] so that the laser beam It is preferable to set the flatness of the transparent member and the polygon mirror. Furthermore, it is preferable to set the flatness such that the radius of curvature of the laser beam transmitting member in the main scanning direction is 200 [m] or less. Further, it is preferable that the flatness of the polygon mirror is set to 0.70 [μm] or less.

Further, since the laser beam transmitting member transmits both the laser beam from the light source and the laser beam reflected by the polygon mirror, an optical scanning device using an inexpensive laser beam transmitting member can be provided.

Further, by disposing the reflecting surfaces of the polygon mirror in a plurality of steps so as to be separated from each other in the rotation axis direction, the positional deviation of each image corresponding to each beam can be reduced and the color deviation in the main scanning direction can be suppressed. A possible optical scanning device can be provided.

Further, as another invention, the above optical scanning device is used in an image forming apparatus for forming a latent image on a latent image carrier by optical scanning and visualizing the latent image to obtain a desired recorded image. Therefore, it is possible to provide an inexpensive image forming apparatus that can realize an image with less jitter and color misregistration.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION According to an optical scanning device in which a laser beam emitted from a light source is deflected and scanned by a polygon mirror and condensed toward a surface to be scanned by a scanning and imaging optical system, the scanning and imaging optical system The feature is that a laser beam transmitting member is provided between the optical paths. Further, the flatness shape of the reflecting surface of the polygon mirror is substantially the same for each surface.

[0018]

1 is a perspective view showing the structure of an optical scanning device according to an embodiment of the present invention. In the figure, a laser light source device 101 emits a plurality of laser beams. It should be noted that, for the sake of convenience, only one laser beam emitted from the light source device 101 is drawn and two laser beams are drawn on the photoconductor 102 in FIG. Each radiated laser beam (substantially parallel beam) enters a cylindrical lens 103 as a line image forming optical system. The cylindrical lens 103 has a positive power only in the sub-scanning direction, focuses the incoming laser beams only in the sub-scanning direction, and forms a long line image in the main scanning direction near the reflecting surface 104a of the polygon mirror 104. To form an image. An actual line image is formed for each laser beam, and the line images are separated from each other in the sub-scanning direction. Then, when the polygon mirror 104 is rotated at a constant speed in the direction of the arrow by a motor unit (not shown), the plurality of laser beams reflected by the reflecting surface 104a become deflection laser beams and are deflected at a constant angular velocity.
Each deflected laser beam passes through the laser beam transmitting member 105 while being deflected, and the fθ lens 1 as a scanning image forming optical system is provided.
When the light beam is incident on 06 and transmitted through the fθ lens 106, it is reflected by the folding mirror 107, which is a long plane mirror, and the optical path is bent, and the action of the fθ lens 106 on the peripheral surface of the photoconductor 102, which is the substance of the surface to be scanned. To collect as a laser spot. Spots of a plurality of laser beams formed on the surface to be scanned are separated from each other in the sub-scanning direction,
As shown in the figure, a plurality of lines on the surface to be scanned are simultaneously scanned by scanning with one reflecting surface. Folding mirror 107
In the vicinity of the scanning start side end in the longitudinal direction of the plane mirror 10
8 are arranged. The portion where the plane mirror 108 is arranged is outside the effective deflection area necessary for the deflection laser beam to scan the effective scanning area of the surface to be scanned. The deflected laser beam reflected by the plane mirror 108 is incident on a photo sensor 109 which is a light receiving means for detecting synchronous light. That is,
Each deflected laser beam first enters the plane mirror 108 and is reflected, and then enters the photosensor 109 and is received on the way to the scanning region of the surface to be scanned while being deflected. The light receiving surface of the photo sensor 109 is arranged at a position optically equivalent to the surface to be scanned. Since each deflected light beam incident on the plane mirror 108 is subjected to the optical action of the fθ lens 106, each deflected laser beam is condensed on the light receiving surface of the photosensor 109 as a light spot similar to that on the surface to be scanned. In this embodiment, the plane mirror 108 and the photo sensor 109 constitute so-called synchronous light detecting means. The flatness shape of the polygon mirror reflecting surface 104a is shown in FIG.
As shown in FIG. 3, each surface has a curved shape, and the entire surface (6 surfaces in FIG. 3) has a concave or convex shape. The hatching area is shown on the polygon mirror center side.
The reflecting surface 10 of FIG. 2A showing a top view of the polygon mirror.
Part of 4a that contributes to laser deflection (effective range: excluding parts such as burrs at corners that occur during machining outside the effective range)
2 (b) and 2 (c) show an example of the planar shape of FIG. Actually, there are slight irregularities (surface roughness component), but only the bending component relating to the deflection scanning accuracy of the laser beam is shown. As can be seen from FIG. 2B, the reflecting surface 104
a has a so-called concave shape, and both ends X of the effective range,
The shape (Z portion) is recessed toward the center side of the line connecting Y. Similarly, as can be seen from FIG. 2C, the reflective surface 1
04a has a so-called convex shape and has both ends X2 and Y2.
It has a convex shape (Z2 portion) on the outer diameter side of the line connecting the two. As described above, the shape of the conventional polygon mirror is such that unevenness is mixed on each surface, or a part of the surface or the entire surface is corrugated (irregularity within one surface), and the flatness is 0.1 to 10. 0.1
5 μm is common. In order to achieve a small diameter beam spot of 50 μm or less (1 / e ² , hereinafter the same) in the conventional mirror shape (concavities and convexities are mixed on each surface, part of the surface or the entire surface is corrugated), it is 0. Flatness of 1 μm or less is required. However, it is difficult to stably process the flatness of 0.1 μm or less, and it is inevitable to increase the cost due to the deterioration of the yield.

Therefore, by aligning the reflecting surfaces of the polygon mirror with concave or convex shapes over the entire surface as in the present invention, the deviation in the main scanning direction can be made the same direction with respect to the regular position, and therefore, substantially. The amount of deviation can be reduced. On the other hand, if the deviation amount is the same, the flatness allowable range can be widened. D and D2 in the figure represent the flatness, both of which are 0.16 μm and may be larger than the conventional flatness. However, the upper limit of flatness is 0.70
It is preferable that the thickness is μm. This is because when the flatness is 0.7 μm or more, the variation of each surface is likely to be large and exceeds the allowable range of correction by the scanning lens, and the deviation amount in the main scanning direction becomes large. The flatness values are measured with a laser interferometer (manufactured by Zygo Co.), and PV (Peak to Valley) values are shown.

FIG. 3 is a sectional view showing the main scanning sectional shape of the laser beam transmitting member of FIG. Conventionally, both surfaces (polygon mirror side, scanned surface side) required high-precision flatness with a radius of curvature exceeding 200 m, but a laser beam transmitting member is provided so as to cancel the power of the polygon mirror in the main scanning direction. Since the power of 105 is set, the flatness of 200 m or less may be used in the present invention. Specifically, the power after cancellation is set to be 4 × 10 ⁻⁶ [1 / mm] or less. This is because if it exceeds 4 × 10 ⁻⁶ [1 / mm], the allowable range for correction by the scanning lens will be exceeded. For example, the flatness of the polygon mirror is 0.16
The power of the polygon mirror is 6.4 × 10 ⁻⁶ [1 / mm] when the concave surface is μm (effective area is 20 mm), and thus the laser transmission member 105 is 2.4 × 10 ⁻⁶ [1 / mm].
With the above power, the power of the polygon mirror is offset. Similarly, the flatness of the polygon mirror is 0.70.
The power of the polygon mirror is 2.8 × 10 ⁻⁵ [1 / mm] when the concave surface is μm (effective area is 20 mm), and thus the laser transmission member 105 is 2.4 × 10 ⁻⁵ [1 / mm].
Those having the above power are arranged. Ideally, it is most preferable to completely cancel the powers of the polygon mirror and the laser transmission member and combine them to cancel the powers. The above power is calculated by the following relational expression.

Power of laser transmitting member: P1 = 1 / n
(1 / R1-1 / R2) [1 / mm] Note that n: refractive index = 1.5, R1: radius of curvature on polygon mirror side [1 / mm], R2: radius of curvature on scanned surface side [1
/ Mm]. Polygon mirror: P2 = 2 / Rm [1 / mm] Note that Rm = {(L / 2) ² + D ² } / 2D, Rm: radius of curvature [1 / mm], D: flatness [mm], L: It is an effective range [mm] in the main scanning direction.

Therefore, as described above, | P1-P2 |
It suffices to set the flatness of the polygon mirror and the laser transmission member so that <4 × 10 ⁻⁶ [1 / mm]. Here, as the material of the laser transmitting member 105, float glass or optical resin is suitable. Float glass has a small thermal expansion and a small change in optical characteristics due to a temperature change, and therefore is particularly suitable when exposed to a high temperature / low temperature environment. On the other hand, since the optical resin can be molded, it is possible to manufacture an arbitrarily small radius of curvature at low cost and to realize cost reduction. Further, in FIG. 1, the laser transmission member transmits the laser beam after being deflected by the polygon mirror, but the laser beam incident on the polygon mirror may be transmitted as a part of the cover covering the polygon mirror. In other words, the laser beam transmitting member is integrally fixed to the cover that covers the polygon mirror, and the bearing has a substantially sealed structure, which facilitates resin molding of the cover material and allows complicated shapes such as the shape of the cover and the laser transmission. It is possible to combine spherical or aspherical parts at a low cost, and it is possible to prevent dust and other dust from entering the dynamic pressure bearings used in high-speed polygon scanners that exceed 30,000 rpm. A high optical scanning device can be provided. The flatness of the laser beam transmitting member 105 is applied to at least the range 110 in the main scanning direction required for image formation by the laser beam deflectively scanned as shown in FIG.

FIG. 4 is a sectional view showing an embodiment of a polygon scanner used in the image forming apparatus of the present invention. The polygon scanner 400 shown in the figure is a dynamic pressure air bearing type polygon scanner that rotates at 30,000 rpm or more. A flange 402 made of an aluminum alloy having a polygon mirror portion 402a is fixed to the outer periphery of a cylindrical rotary sleeve 401 made of ceramic by shrink fitting. Above the rotating body A, a rotating yoke 403 (made of a magnetic body) that constitutes a magnetic bearing is fixed to the center of a closing member 404 made of an aluminum alloy. The closing member 404 is the flange 402.
Is fixed to the upper portion of the rotary sleeve 401 by press fitting, heat shrinkage or adhesion, and also has a function of closing the upper end open portion of the rotary sleeve 401. A rotor magnet 405 is arranged below the flange 402, and constitutes a brushless motor of an outer rotor type together with a stator core 406 facing each other in the circumferential direction.
The circumferential groove 402b provided on the flange 402 is for preventing stress strain on the polygon mirror portion when the sleeve 401 and the closing member 404 are fixed or the temperature rises. The fixed shaft 407 constituting the radial dynamic pressure bearing is made of a cylindrical ceramic material like the rotary sleeve 401, and has a herringbone dynamic pressure generating groove 407a formed on the outer diameter surface. The rotary sleeve 401
The dynamic pressure bearing gap formed with the inner peripheral surface of the is fitted with a gap of several μm. In addition, by integrating the polygon mirror and the bearing member that supports it rotatably by shrink-fitting, the reflecting surface of the polygon mirror formed on the concave or convex surface is not deformed, and the laser beam position in the main scanning direction is eliminated. It is possible to provide a polygon scanner that can reduce the deviation and that does not deteriorate the balance of the rotating body even at high temperature and high speed rotation of 30000 rpm or more, and has less vibration.

In addition, a permanent magnet assembly for a magnetic bearing (magnet 40, which constitutes an axial bearing, is provided on the inner peripheral portion of the fixed shaft 407.
8+ the upper and lower magnetic plates 409, 410) are arranged. The magnetic bearing permanent magnet assembly has a magnetic gap in the radial direction with respect to the protrusion 403a of the rotating yoke 403 of the magnetic body, and supports the magnetic bearing in the axial direction in a non-contact manner by utilizing the attractive force acting between the gaps. Further, the air pocket 411 formed by the fixed shaft 407 and the rotary body A has a fine hole for communicating the upper air pool 411 with the outside of the rotary body A, such as the magnetic rotation yoke 403 or the lower closing member or the closing member 404. Is formed (not shown) on the member forming the magnetic field, and the magnetic bearing has a damping characteristic. Further, the rotating body A includes a motor housing 412 and an upper cover 4 so as to cover the rotating body.
13 and the laser beam transmitting member 105 are substantially sealed.

Further, the balance of the rotating body A is corrected in order to reduce the vibration during high speed rotation. In order to realize low vibration at high speed rotation of 40,000 rpm or more, the unbalance amount of the rotating body A needs to be 10 mg · mm or less, and for example, the correction amount must be 1 mg or less at a radius of 10 mm. Become. The correction points are two points in the axial direction of the upper and lower parts of the rotating body, and it is preferable to arrange the upper and lower two points so as to sandwich the center of rotation weight. It should be noted that when performing a slight correction of 1 mg or less, it is difficult to control an adhered matter such as an adhesive, and since the amount is small, the adhesive force is weak and peels and scatters at a high speed rotation of 40,000 rpm or more. In this respect, a method of removing a part of the parts of the rotating body (cutting with a drill or laser processing) is preferable because the above-mentioned trouble does not occur. For driving the motor, the magnetic field of the rotor magnet 405 refers to a signal output from the Hall element 415 mounted on the motor substrate 414 as a position signal, and the drive circuit switches the excitation of the stator winding to rotate. here,
The rotor magnet 405 is magnetized in the radial direction, and rotates with the outer circumference of the stator core 406 to generate a rotational torque. The rotor magnet 405 has a magnetic path open in the outer diameter other than the inner diameter and in the height direction, and the Hall element 415 for switching the excitation of the motor is arranged in the open magnetic path. Magnetic material 416
Has a function of shielding the leakage magnetic flux from the rotor magnet 405, and prevents the eddy current from flowing in the housing 412. At least the rotary sleeve 401 and the flange 402 are fixed by shrinking after the rotating sleeve 401 and the flange 402 are fixed. It is mirror-finished. The mirror surface processing is performed with high precision based on the inner diameter or the upper end surface or the lower end surface of the rotary sleeve 401. When the end surface of the rotary sleeve 401 is used as a reference, it is necessary to process the deflection with respect to the center of the inner diameter with high accuracy of 5 μm or less in advance. This runout accuracy is the flatness during mirror finishing,
This is because the trouble quality is affected. The diameter of the rotating body A is smaller than the inscribed circle diameter except for the polygon mirror reflection surface portion. For example, the diameter may be as small as 0.1 mm or more. The reason is to avoid the tip of the cutting tool (cutting tool) from colliding with the outer diameter portion of the rotating member during mirror finishing. Since the mirror surface processing is performed in this step, the polygon mirror does not need to be fixed by a separate component such as a leaf spring, and the flatness of the polygon mirror processed with high precision due to the fixing is not deteriorated. Further, it is no longer necessary to make the flatness and squareness of the polygon mirror mounting surface highly accurate for each component, which has been conventionally required to maintain the surface tilt characteristic.

Further, the rotor magnet 405 is a bond magnet using a resin as a binder, and the flange 402 holds the outer diameter so that the outer diameter portion of the rotor magnet 405 is not broken by centrifugal force during high-speed rotation. It is a structure. The rotor magnet 405 is press-fitted and fixed. In order to prevent the dynamic pressure bearing and the polygon mirror from being damaged by dust and to prevent the wind noise of the high-speed rotating polygon mirror, a substantially sealed structure is formed by the motor housing 412, the upper lid 413 and the laser beam transmitting member 105. There is. The motor housing 412 and the upper lid 413 are made of a metal member (in particular, an aluminum alloy having a high thermal conductivity is suitable), and it is possible to quickly transmit a temperature rise due to heat generation of the polygon scanner 400 to the optical housing. .

The polygon scanner 400 having such a configuration is detachably fixed to the optical housing by screwing to a fixing portion 417 provided on the outer wall of the motor housing 412. The optical housing is also made of a heat-dissipating aluminum alloy, and the heat transmitted from the polygon scanner 400 can be quickly dissipated to the outside. Therefore, it is possible to use an inexpensive plastic lens that has been a problem with respect to temperature rise. By making the polygon scanner 400 detachable from the optical housing, even if the polygon scanner 400 fails, it can be replaced in units of polygon scanners.
In the case of a polygon scanner whose rotation speed is low and temperature rise does not matter as in pm or less, a resin motor housing can be adopted without considering heat dissipation and an optical scanning device that can be commonly used for optical housings etc. Can be provided.

FIG. 5 is a sectional view showing another embodiment of the polygon scanner used in the image forming apparatus of the present invention. The embodiment shown in the figure is an example in which the cover 501 that covers the mirror of the polygon scanner is formed of a laser-transmissive material having the above power. In this case, the cover material is preferably a resin that can arbitrarily have a complicated shape (a combination of the shape of the cover portion and the spherical surface or aspherical surface of the laser transmitting portion). Also,
It can be manufactured at low cost by using resin molding.

FIG. 6 is a cross-sectional view showing an example of a polygon scanner used in a full-color image forming optical scanning device in which a plurality of laser beams separated vertically in the axial direction are incident. The polygon mirror portions 601a, 601b, 601c, and 601d that are separated from each other in the axial direction of the polygon scanner 600 have a plurality of laser beams A, B, and C corresponding to the respective colors.
D is incident on each of the four surfaces that are axially opposed to each other, and high-speed deflection scanning is performed. In this case, it is preferable that the upper and lower reflecting surfaces have the same shape, as described above. This is because if the concave and convex shapes of the reflecting surfaces that are vertically separated are different, a deviation occurs for each color image corresponding to each beam, and a color deviation in the main scanning direction occurs.

Next, FIG. 7 is a schematic sectional view showing the structure of an image forming apparatus according to another embodiment of the invention. In the figure, a photoconductive photoconductor 701 as a latent image carrier is formed in a cylindrical shape and rotates at a constant speed in the direction of the arrow, and the charging means 70 is formed.
2 is uniformly charged, and an electrostatic latent image is formed by writing by optical scanning of the optical scanning device 703. The formed electrostatic latent image is developed by the developing unit 704, and the toner image obtained by the development is transferred to the sheet-shaped recording medium (transfer paper, plastic sheet for overhead projector, etc.) 706 by the transfer unit 705. . The recording medium 706 is
The transferred toner image is fixed by the fixing unit 707 composed of a pair of fixing rollers, and is discharged to the outside of the apparatus. The photoconductor 701 after the toner image transfer is cleaned by a cleaning device 708.
As a result, residual toner, paper dust, etc. are removed. As the optical scanning device 703, the optical scanning device shown in FIG. 1 is used. That is, the image forming apparatus shown in FIG. 7 forms a latent image on a latent image carrier by optical scanning and visualizes the latent image to obtain a desired recorded image. In the image forming apparatus, the latent image carrier is optically scanned. As the optical scanning device, the optical scanning device of FIG. 1 is used, and the latent image carrier is a photoconductive photoconductor 701.
An electrostatic latent image is formed by the uniform charging and optical scanning, and the formed electrostatic latent image is visualized as a toner image.

It is needless to say that the present invention is not limited to the above embodiments, and various modifications and substitutions can be made within the scope of the claims.

[0032]

As described above, the laser beam emitted from the light source is deflected and scanned by the polygon mirror,
The optical scanning device in which the scanning and imaging optical system focuses light toward the surface to be scanned is characterized in that a laser beam transmitting member is provided between the optical paths of the scanning and imaging optical system. Therefore, an image with less jitter and color misregistration can be realized without increasing the precision of the polygon mirror flatness.

Further, since the flatness shape of the reflecting surface of the polygon mirror is substantially the same for all the surfaces, the laser beam position shift in the main scanning direction can be reduced without increasing the precision of the polygon mirror flatness. This makes it possible to realize images with less jitter and color misregistration.

Further, it is preferable that the flatness of the reflecting surface of the polygon mirror is substantially concave or convex.

Further, it is preferable that the flatness shape of the laser beam transmitting member in the main scanning direction is substantially concave or convex.

Further, since the flatness of each flatness shape of the polygon mirror and the laser beam transmitting member is within the effective range corresponding to the scanned surface area, the precision of the reflecting surface of the polygon mirror is increased more than necessary. You do n’t need
An inexpensive optical scanning device can be provided.

When the powers of the laser beam transmitting member and the polygon mirror in the main scanning direction are P1 and P2, respectively, | P1-P2 | <4 × 10 ⁻⁶ [1 / mm] It is preferable to set the flatness of the transparent member and the polygon mirror. Furthermore, it is preferable to set the flatness such that the radius of curvature of the laser beam transmitting member in the main scanning direction is 200 [m] or less. Further, it is preferable that the flatness of the polygon mirror is set to 0.70 [μm] or less.

Further, since the laser beam transmitting member transmits both the laser beam from the light source and the laser beam reflected by the polygon mirror, an optical scanning device using an inexpensive laser beam transmitting member can be provided.

Further, by disposing the reflecting surfaces of the polygon mirror in a plurality of steps spaced apart from each other in the direction of the rotation axis, the positional deviation for each image of each color corresponding to each beam can be reduced and the color deviation in the main scanning direction can be suppressed. A possible optical scanning device can be provided.

Further, as another invention, the above optical scanning device is used in an image forming apparatus for forming a latent image on a latent image carrier by optical scanning and visualizing the latent image to obtain a desired recorded image. Therefore, it is possible to provide an inexpensive image forming apparatus that can realize an image with less jitter and color misregistration.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration of an optical scanning device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a flatness shape of a polygon mirror reflecting surface.

3 is a sectional view showing a main scanning sectional shape of the laser beam transmitting member of FIG.

FIG. 4 is a sectional view showing an embodiment of a polygon scanner used in the image forming apparatus of the present invention.

FIG. 5 is a sectional view showing another embodiment of the polygon scanner used in the image forming apparatus of the present invention.

FIG. 6 is a cross-sectional view showing another embodiment of the polygon scanner used in the image forming apparatus of the present invention.

FIG. 7 is a schematic cross-sectional view showing the configuration of an image forming apparatus according to another embodiment of the invention.

[Explanation of symbols]

Reference numeral 104; polygon mirror; 104a; polygon mirror reflection surface; 105; laser beam transmitting member.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2C362 AA07 AA10 BA05 BA48 BA53                       BA68 BA83 BA85                 2H045 AA03 AA05 AA34                 5C051 AA02 CA07 DB22 DB30                 5C072 AA03 DA02 DA04 DA20 DA21                       HA02 HA09 HA13 HA20 XA05

Claims (11)

[Claims] 1. An optical scanning device in which a laser beam emitted from a light source is deflected and scanned by a polygon mirror and condensed by a scanning and imaging optical system toward a surface to be scanned, wherein an optical path is provided between the optical paths of the scanning and imaging optical system. An optical scanning device comprising a laser beam transmitting member. 2. The optical scanning device according to claim 1, wherein the flatness shape of the reflecting surface of the polygon mirror is substantially the same for each surface. 3. The optical scanning device according to claim 2, wherein the flatness shape of the reflecting surface of the polygon mirror is a substantially concave surface or a substantially convex surface. 4. The optical scanning device according to claim 1, wherein the flatness shape of the laser beam transmitting member in the main scanning direction is substantially concave or convex. 5. The optical scanning device according to claim 3, wherein the flatness of each flatness shape of the polygon mirror and the laser beam transmitting member is within an effective range corresponding to a scanned surface area. 6. When the powers of the laser beam transmitting member and the polygon mirror in the main scanning direction are P1 and P2, respectively, | P1−P2 | <4 × 10 ⁻⁶ [1 / mm], The optical scanning device according to claim 1, wherein flatness of the laser beam transmitting member and the polygon mirror is set. 7. The optical scanning device according to claim 6, wherein the flatness is such that the radius of curvature of the laser beam transmitting member in the main scanning direction is 200 [m] or less. 8. The flatness of the polygon mirror is 0.70.
The optical scanning device according to claim 6, wherein the optical scanning device is set to be [μm] or less. 9. The optical scanning device according to claim 1, wherein the laser beam transmitting member transmits both the laser beam from the light source and the laser beam reflected by the polygon mirror. 10. The optical scanning device according to claim 1, wherein the reflection surface of the polygon mirror is provided in a plurality of stages spaced apart in the rotation axis direction. 11. An image forming apparatus for forming a latent image on a latent image carrier by optical scanning and visualizing the latent image to obtain a desired recorded image, wherein the light according to any one of claims 1 to 10 is used. An image forming apparatus using a scanning device.