JP2010072050A - Optical scanner and method of adjusting optical scanner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an optical scanner in which a color shift in a sub scanning direction is reduced, a color shift in a main scanning direction is also reduced and a precise image is obtained, and to obtain a method of adjusting the optical scanner. <P>SOLUTION: The optical scanner includes: a plurality of light source means; incident optical systems which guide a plurality of luminous fluxes emitted from the plurality of light source means to deflection means; and imaging optical systems which are provided correspondingly to respective faces to be scanned for imaging the plurality of luminous fluxes deflected and scanned by the deflection faces of the deflection means to the corresponding plurality of faces to be scanned, respectively, wherein a plurality of reflection mirrors are disposed in at least one optical path between the deflection means and the face to be scanned. The optical scanner further includes: an adjustment means which adjusts a scanning line curvature by bending the reflection face of a first reflection mirror which has a maximum incident angle of the luminous flux among the plurality of reflection mirrors; and an adjustment means which adjusts the whole magnitude by bending the reflection face of a second reflection mirror which has the smallest incident angle of the luminous flux among the plurality of reflection mirrors. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical scanning device and a method for adjusting the optical scanning device, and is suitable for, for example, a laser beam printer having an electrophotographic process, a digital copying machine, and a color image forming apparatus of a multifunction printer (multifunction printer).

  2. Description of the Related Art Conventionally, an optical scanning device used in an image forming apparatus such as a laser beam printer, a digital copying machine, or a multi-function printer uses an optical deflector (polygon mirror) as a deflecting unit for a light beam emitted from a light source unit by an incident optical system. ). The light beam deflected and scanned by the optical deflector is imaged in a spot shape on the surface of the photosensitive drum, which is the surface to be scanned, by the imaging optical system, and the surface of the photosensitive drum is optically scanned with the light beam.

  In such an optical scanning device, the light beam emitted from the light source means is converted into a parallel light beam by a collimator lens or the like, and the light beam converted into a parallel light beam for correcting tilt is applied to the deflecting surface of the optical deflector by a cylindrical lens. A line image is formed. The light beam deflected and scanned by the deflecting surface of the optical deflector scans the surface of the photosensitive drum at a constant speed via the imaging lens to form a spot on the surface to be scanned.

  FIG. 22 is a schematic view of a main part of a conventional color image forming apparatus.

  In the figure, reference numerals 91a, 91b, 91c, and 91d denote light source means, which are made of, for example, a semiconductor laser. Reference numeral 92 denotes an optical deflector as a deflecting means, which is composed of, for example, a rotating polygon mirror, and is rotated at a constant speed in the direction of arrow A in the figure by a driving means (not shown) such as a motor. An imaging optical system having an fθ characteristic (not shown) has a conjugate relationship between the deflecting surfaces 92a and 92b of the optical deflector 92 and the photosensitive drum surfaces 100a, 100b, 100c, and 100d as scanned surfaces in the sub-scan section. It has a tilt correction function. The latent images formed on the photosensitive drum surfaces 100a, 100b, 100c, and 100d become an image in which four colors are superimposed on the intermediate transfer belt 90, and transferred onto a transfer sheet (not shown).

  In addition, the color image forming apparatus in the figure is provided with a folding mirror for folding the optical path in the optical path between the optical deflector 92 and the photosensitive drum surfaces 100a, 100b, 100c, and 100d in order to make the entire apparatus compact. As a result, downsizing has been achieved.

  In an optical scanning device used in this type of image forming apparatus, for example, when correcting a scanning line bending (scanning line bending) of a scanning line on a surface to be scanned, which occurs due to a position error of an imaging optical element, or the like. Is done as follows. That is, in order to correct the curvature of the scanning line in the sub-scanning direction, the longitudinal direction (Y direction) of the bending mirror in the optical path of the imaging optical system is curved to correct the scanning line curvature.

  Usually, in a color image forming apparatus having a scanned surface for a plurality of colors (for example, C (cyan), M (magenta), Y (yellow), B (black)), the amount of bending between the plurality of scanned surfaces is set. It is known to match and reduce color misregistration.

  However, when the bending mirror is curved as described above, the curvature in the sub-scanning direction is corrected, but the overall magnification (image length) in the main scanning direction is also shifted.

Therefore, in recent years, the shape in the longitudinal direction of the bending mirror (reflecting mirror) arranged in the optical path between the optical deflector and the surface to be scanned is curved (bent) in the normal direction of the reflecting surface and the sub-scanning direction. Various optical scanning devices have been proposed that correct the scanning line bending (see Patent Documents 1 and 2).
JP 2005-265904 A Japanese Patent No. 3709727

  Usually, in order to correct the scanning line bending in the sub-scanning direction using a bending mirror, the deflection amount (adjustment amount) can be controlled by the following parameters.

(1) Deflection amount of bending mirror,
(2) The incident angle of the light beam incident on the bending mirror.

  Conventionally, as disclosed in Patent Document 1, an optical scanning device having a function of correcting a scanning line curve has a configuration in which the scanning line curve of another station matches the station (color) having the largest scanning line curve. ing. In addition, the optical scanning device disclosed in Patent Document 2 is configured to generate a large scanning line curve in an initial state and to deflect a mirror in one direction to reduce color misregistration.

  However, in the conventional optical scanning devices described in Patent Documents 1 and 2, the color shift in the sub-scanning direction is corrected by the adjusting means for adjusting the scanning line curve, but by correcting the color shift in the sub-scanning direction. It is difficult to correct the deteriorated color shift in the main scanning direction by optical means.

  Even if the color deviation in the main scanning direction is not caused by the adjustment means for adjusting the scanning line curvature, the color deviation in the main scanning direction due to the mounting error of the optical components such as the lens and the mirror and the environmental variation is optically detected. It is difficult to correct. Therefore, there is a problem that it is difficult to increase the definition of the image due to the displacement of the printing position in the main scanning direction.

  In recent years, a method of electrically correcting a printing position shift in the main scanning direction has also been adopted. However, such correction tends to make it difficult to perform highly accurate correction when the entire apparatus becomes complicated and the correction amount is large.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an optical scanning device and a method for adjusting the optical scanning device that can obtain a high-definition image that can reduce color misregistration in the sub-scanning direction and can also reduce color misregistration in the main scanning direction.

The optical scanning device of the invention of claim 1
A plurality of light source means;
An incident optical system for guiding a plurality of light beams emitted from the plurality of light source means to a deflecting means;
An imaging optical system provided corresponding to each scanned surface for imaging a plurality of light beams deflected and scanned by the deflection surface of the deflecting unit on a plurality of corresponding scanned surfaces;
An optical scanning device comprising:
A plurality of reflecting mirrors are disposed in at least one optical path between the deflecting means and the surface to be scanned, and the reflection of the first reflecting mirror having the largest incident angle of the light beam among the plurality of reflecting mirrors. Adjusting means for adjusting the scanning line curve by bending the surface, and adjusting means for adjusting the overall magnification by bending the reflecting surface of the second reflecting mirror having the smallest incident angle of the light beam among the plurality of reflecting mirrors. It is characterized by.

The invention of claim 2 is the invention of claim 1,
When the scanning line curvature sensitivity of the first and second reflecting mirrors is V1 and V2, respectively, and the overall magnification sensitivity of the first and second reflecting mirrors is M1 and M2,
V2 / V1 ≦ 0.5
M2 / M1 ≧ 0.7
It is characterized by satisfying the following conditions.

An optical scanning device according to a third aspect of the present invention comprises:
A plurality of light source means;
An incident optical system for guiding a plurality of light beams emitted from the plurality of light source means to a deflecting means;
An imaging optical system provided corresponding to each scanned surface for imaging a plurality of light beams deflected and scanned by the deflection surface of the deflecting unit on a plurality of corresponding scanned surfaces;
An optical scanning device comprising:
A plurality of reflecting mirrors are disposed in at least one optical path between the deflecting means and the surface to be scanned, and the reflecting surface of the reflecting mirror having the smallest incident angle of the light beam among the plurality of reflecting mirrors is arranged. First adjusting means for adjusting the overall magnification by bending, and second adjusting means for adjusting the scanning line curve by decentering a part of the imaging optical elements constituting the imaging optical system. It is characterized by that.

An optical scanning device according to a fourth aspect of the invention comprises
A plurality of light source means;
An incident optical system for guiding a plurality of light beams emitted from the plurality of light source means to a deflecting means;
An imaging optical system provided corresponding to each scanned surface for imaging a plurality of light beams deflected and scanned by the deflection surface of the deflecting unit on a plurality of corresponding scanned surfaces;
An optical scanning device comprising:
A plurality of reflecting mirrors are arranged in at least one optical path between the deflecting means and the surface to be scanned, and the first reflecting mirror having the highest scanning line curvature sensitivity among the plurality of reflecting mirrors. Adjusting means for adjusting the scanning line curve by bending the reflecting surface; and adjusting means for adjusting the overall magnification by bending the reflecting surface of the second reflecting mirror having the smallest incident angle of the light beam among the plurality of reflecting mirrors; It is characterized by having.

The image forming apparatus of the invention of claim 5
A plurality of image carriers that are arranged on a surface to be scanned of the optical scanning device according to any one of claims 1 to 4 and that form images of different colors.

The invention of claim 6 is the invention of claim 5,
It is characterized by having a printer controller that converts color signals input from an external device into image data of different colors and inputs them to each optical scanning device.

An adjustment method for an optical scanning device according to a seventh aspect of the invention comprises:
A plurality of light source means;
An incident optical system for guiding a plurality of light beams emitted from the plurality of light source means to a deflecting means;
An imaging optical system provided corresponding to each scanned surface for imaging a plurality of light beams deflected and scanned by the deflection surface of the deflecting unit on a plurality of corresponding scanned surfaces;
A method of adjusting an optical scanning device having:
A plurality of reflecting mirrors are disposed in at least one optical path between the deflecting means and the surface to be scanned, and the reflection of the first reflecting mirror having the largest incident angle of the light beam among the plurality of reflecting mirrors. The scanning line curve is adjusted by bending the surface, and the overall magnification is adjusted by bending the reflecting surface of the second reflecting mirror having the smallest incident angle of the light beam among the plurality of reflecting mirrors.

The invention of claim 8 is the invention of claim 7,
When the scanning line curvature sensitivity of the first and second reflecting mirrors is V1 and V2, respectively, and the overall magnification sensitivity of the first and second reflecting mirrors is M1 and M2,
V2 / V1 ≦ 0.5
M2 / M1 ≧ 0.7
It is characterized by satisfying the following conditions.

An adjustment method for an optical scanning device according to a ninth aspect of the invention comprises:
A plurality of light source means;
An incident optical system for guiding a plurality of light beams emitted from the plurality of light source means to a deflecting means;
An imaging optical system provided corresponding to each scanned surface for imaging a plurality of light beams deflected and scanned by the deflection surface of the deflecting unit on a plurality of corresponding scanned surfaces;
A method of adjusting an optical scanning device having:
A plurality of reflecting mirrors are disposed in at least one optical path between the deflecting means and the surface to be scanned, and the reflecting surface of the reflecting mirror having the smallest incident angle of the light beam among the plurality of reflecting mirrors is arranged. The entire magnification is adjusted by bending, and a part of the imaging optical elements constituting the imaging optical system is decentered to adjust the scanning line curvature.

The adjustment method of the optical scanning device of the invention of claim 10 is as follows:
A plurality of light source means;
An incident optical system for guiding a plurality of light beams emitted from the plurality of light source means to a deflecting means;
An imaging optical system provided corresponding to each scanned surface for imaging a plurality of light beams deflected and scanned by the deflection surface of the deflecting unit on a plurality of corresponding scanned surfaces;
A method of adjusting an optical scanning device having:
A plurality of reflecting mirrors are arranged in at least one optical path between the deflecting means and the surface to be scanned, and the first reflecting mirror having the highest scanning line curvature sensitivity among the plurality of reflecting mirrors. The scanning surface curve is adjusted by deflecting the reflecting surface, and the overall magnification is adjusted by bending the reflecting surface of the second reflecting mirror having the smallest incident angle of the light beam among the plurality of reflecting mirrors. .

  According to the present invention, it is possible to achieve an optical scanning apparatus and an optical scanning apparatus adjustment method capable of obtaining a high-definition image that can reduce color misregistration in the sub-scanning direction and also reduce color misregistration in the main scanning direction. it can.

  The optical scanning device according to the present invention includes a plurality of light sources, a first optical means for guiding the light beams from the light source means to the deflecting means, and a plurality of light beams deflected and scanned by the deflection surfaces of the deflecting means. And second optical means provided corresponding to each scanned surface for forming an image on the scanned surface.

  Further, a plurality of reflecting mirrors are arranged in at least one optical path between the deflecting means and the surface to be scanned. Then, among the plurality of reflecting mirrors, the reflecting surface of the first reflecting mirror having the largest incident angle of the light beam is deflected to adjust the scanning line curve, and the reflecting surface of the second reflecting mirror having the smallest incident angle of the light beam is deflected. The overall magnification is adjusted.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a cross-sectional view (sub-scanning cross-sectional view) of the main part in the sub-scanning direction in the image forming apparatus of Embodiment 1 of the present invention.

  In the following description, the sub-scanning direction (Z direction) is a direction parallel to the rotation axis of the deflecting means. The main scanning section is a section whose normal is the sub-scanning direction (direction parallel to the rotation axis of the deflecting means). The main scanning direction (Y direction) is the direction in which the light beam deflected and scanned by the deflecting means is projected onto the main scanning section. The sub-scanning cross section is a cross section whose normal is the main scanning direction.

  The image forming apparatus in this embodiment includes an optical deflector 5a, two optical scanning devices (stations) S1 and S2, which share the optical deflector 5a, an optical deflector 5b, and the optical deflector 5b. There are two optical scanning devices (stations) S3 and S4 used in common. The plurality of light beams deflected and scanned by the optical deflectors 5a and 5b are scanned on the photosensitive drum surfaces 8a, 8b, 8c, and 8d as different scanning surfaces. A color image is formed by multiple development.

  Although two optical deflectors 5a and 5b are shown in FIG. 1, the optical deflectors 5a and 5b are configured in common as shown in FIG. 22, and the optical deflectors 5a and 5b are different from each other. Two light beams are deflected and scanned on the deflecting surface.

  In FIG. 1, 5 (5a, 5b) is an optical deflector (polygon mirror) as a common deflecting means, and is rotated at a constant speed by a driving means (not shown) such as a motor.

Reference numeral 6a (6a ₁ , 6a ₂ ) denotes a first imaging lens (fθ lens) provided in each station S1, S2, S3, S4. 6b (6b ₁ , 6b ₂ , 6b ₃ , 6b ₄ ) is also a second imaging lens (fθ lens) provided in each of the stations S1, S2, S3, S4, and is made by plastic molding.

  In the present embodiment, the first and second imaging lenses 6a and 6b constitute the imaging optical system of each of the stations S1, S2, S3 and S4.

The first imaging lens 6a ₁ is shared by the stations S1 and S2, and the first imaging lens 6a ₂ is shared by the stations S3 and S4.

  Reference numeral 9a denotes a bending mirror (reflection mirror) disposed in the station S1, and reference numerals 9b and 9c each denote a bending mirror (reflection mirror) disposed in the station S2. Reference numeral 9d denotes a bending mirror (reflection mirror) disposed at the station S3, and reference numerals 9e and 9f each denote a bending mirror (reflection mirror) disposed at the station S4.

The plurality of bending mirrors 9a, 9b, 9c, 9d, 9e, 9f are arranged in the downstream optical path from the optical deflector 5 (5a, 5b) to the scanned surface 8 (8a, 8b, 8c, 8d). Has been. In addition, the second imaging lens 6b (6b ₁ , 6b ₂ , 6b ₃ , 6b ₄ ) is disposed on the optical deflector 5 side.

  In this embodiment, the shapes of the reflecting surfaces of the bending mirrors 9a, 9c, 9d, and 9f that are optically closest to the surface to be scanned (downstream from the optical deflector 5) in each of the stations S1, S2, S3, and S4 are long. It bends in the direction (main scanning direction). Thus, in this embodiment, the curvature (scanning line bending) of the scanning line on the scanned surface 8 (8a, 8b, 8c, 8d) in the sub-scanning direction is corrected.

  Bending mirrors 9a, 9c, 9d, and 9f that correct the scanning line bending are mirrors that maximize the incident angle of the light beam in stations S1, S2, S3, and S4, respectively. The mirrors 9a, 9c, 9d, and 9f are hereinafter referred to as “first reflection mirror” or “scanning curve correction mirror”.

  The scanning line curve correcting mirror 9a at the station S1 and the scanning line curve correcting mirror 9d at the station S3 have the same shape. Further, the scanning line curvature correcting mirror 9c of the station S2 and the scanning line curvature correcting mirror 9f of the station S4 have the same shape. Each of the scanning line curvature correcting mirrors 9a, 9c, 9d, and 9f is held so that the reflecting surface is bent into both a concave shape and a convex shape.

  The scanning line curvature correcting mirrors 9a and 9d in the present embodiment are held so that the reflecting surfaces bend in a convex shape. Further, the scanning line curvature correcting mirrors 9c and 9f are held so that the reflecting surface is bent into a concave shape.

  Reference numerals 8a, 8d, 8c, and 8d denote photosensitive drum surfaces (photosensitive drums) as scanning surfaces corresponding to the stations S1, S2, S3, and S4, respectively. Each station S1, S2, S3, S4 constitutes an element of the image forming apparatus.

  M1 and M2 are first and second scanners, respectively. Since the configurations and optical functions of the first and second scanners M1 and M2 in the present embodiment are the same, the following description will focus on the first scanner M1. Of the members of the second scanner M2, the same members as those of the first scanner M1 are shown in parentheses. Then, each member of the second scanner M2 is described as necessary.

  FIG. 2 is a sectional view (main scanning sectional view) of the main part in the main scanning direction of the station S1 shown in FIG. FIGS. 3 and 4 are perspective views of essential parts around the scanning line curvature correcting mirror 9a shown in FIG. The optical action of the other stations S2, S3, S4 is the same as that of the station S1.

  In FIG. 2, reference numeral 1 denotes light source means, which is made of, for example, a semiconductor laser. A light beam conversion element (collimator lens) 2 converts a light beam emitted from the light source means 1 into a parallel light beam (or a divergent light beam or a convergent light beam). Reference numeral 3 denotes a first cylindrical lens having a predetermined power (refractive power) only in the sub-scan section (sub-scan direction). A line image is formed on a deflecting surface 5a1 of an optical deflector 5a described later.

  Reference numeral 4 denotes a second cylindrical lens, which has a predetermined power only in the main scanning section (main scanning direction), converts a parallel light beam that has passed through the collimator lens 2 into a divergent light beam, and corrects wavefront aberration. In addition, the spot shape on the scanned surface 8a is corrected well. Reference numeral 7 denotes a folding mirror that deflects the light beam that has passed through the second cylindrical lens 4 with respect to the main scanning direction and guides it to the optical deflector 5a.

Incidentally, the collimator lens 2, the first, second cylindrical lens 3, 4, and the first elements of the imaging lens 6a ₁ to be described later are components of an input optical system LA.

  Reference numeral 5a denotes an optical deflector (polygon mirror) as a deflecting means having 10 deflecting surfaces, which is rotated at a constant speed in the direction of arrow A in the figure by a driving means (not shown) such as a motor.

LB is an imaging optical system provided for each surface to be scanned, and includes first and second imaging lenses (anamorphic lenses) 6a ₁ and 6b ₁ having different powers in the main scanning section and the sub-scanning section. Have. The imaging optical system LB images a light beam based on image information deflected and scanned by the optical deflector 5a onto a spot on a photosensitive drum surface 8a as a scanned surface in the main scanning section. In addition, a tilt correction function is provided by optically conjugating the deflection surface 5a1 of the optical deflector 5a and the photosensitive drum surface 8a in the sub-scan section. The first imaging lens 6a ₁ constitutes also a part of the input optical system LA.

In this embodiment, the light beam (incident light beam) incident on the optical deflector 5a passes through the _first imaging lens 6a1. The light beam deflected and scanned by the optical deflector 5a (scanned light beam) is again configured to enter the _first imaging lens 6a1.

  Reference numeral 9a denotes a scanning line curvature correcting mirror, which is disposed in the optical path between the optical deflector 5a and the scanned surface 8a, and curves the scanning line on the scanned surface 8a in the sub-scanning direction (scanning line bending). ) Is corrected (adjusted).

  Reference numeral 8a denotes a photosensitive drum surface as a surface to be scanned.

In this embodiment, the light beam modulated and emitted from the semiconductor laser 1 is converted into a parallel light beam by the collimator lens 2, converted into convergent light by the first cylindrical lens 3, and incident on the second cylindrical lens 4. . Of the light beams incident on the second cylindrical lens 4, the light beams in the sub-scanning section converge and pass through the first imaging lens 6 a ₁ (double path configuration) and enter the deflection surface 5 a ₁ of the optical deflector 5 a. A line image (line image elongated in the main scanning direction) is formed on the deflection surface 5a1. At this time, the light beam incident on the deflecting surface 5a1 is a plane perpendicular to the rotational axis of the optical deflector 5a (optical deflector) from the sub-scan section including the rotational axis of the optical deflector 5a and the optical axis of the imaging optical system LB. The light is incident from an oblique direction with a predetermined angle with respect to the rotation plane 5a. Thereby, the incident light beam and the deflected light beam are separated (obliquely incident optical system).

On the other hand, the light beam in the main scanning section diverges and is converted into a parallel light beam by passing through the _first imaging lens 6a1, and is incident on the deflection surface 5a1 from the center of the deflection angle of the optical deflector 5a ( Front incidence). The beam width of the parallel beam at this time is set to be sufficiently wider than the facet width of the deflecting surface 5a1 of the optical deflector 5a in the main scanning direction (overfilled optical system).

The light beam deflected and reflected by the deflecting surface 5a1 of the optical deflector 5a is guided to the photosensitive drum surface 8a through the first imaging lens 6a ₁ , the scanning line curvature correcting mirror 9a, and the second imaging lens 6b _1. Lighted. Then, by rotating the optical deflector 5a in the direction of arrow A, the photosensitive drum surface 8a is optically scanned in the direction of arrow B (main scanning direction). As a result, an image is recorded on the photosensitive drum surface 8a as a recording medium.

In the present embodiment, the shapes of the first and second imaging lenses 6a ₁ and 6b ₁ are expressed by the following mathematical expressions.

  The intersection of the imaging lens surface and the optical axis is the origin, and as shown in FIG. 2, the optical axis is the x axis on the scanning start side and the scanning end side with respect to the optical axis, and is orthogonal to the optical axis in the main scanning section. The y-axis is the direction to perform, and the z-axis is the direction orthogonal to the optical axis in the sub-scanning section, and can be expressed by the following continuous function.

  Scan start side

  End of scanning

R is a radius of curvature, and K, B ₄ , B ₆ , B _{8 and} B ₁₀ are aspherical coefficients.

  In this embodiment, the shape in the main scanning direction is symmetrical with respect to the optical axis, that is, the aspheric coefficients on the scanning start side and the scanning end side are made to coincide.

In the sub-scanning direction scanning start side and the scanning end side with respect to the optical axis, the curvature in the sub-scan section of the second first side of the imaging lens 6b ₁ (plane perpendicular to comprise the main scanning cross section of the optical axis) Are continuously changed in the effective portion of the lens. Further, the shapes in the main scanning direction and the sub-scanning direction are configured symmetrically with respect to the optical axis.

  The shape in the sub-scanning direction is the scanning start side and the scanning end side with respect to the optical axis, the optical axis is the x axis, the direction orthogonal to the optical axis in the main scanning section is the y axis, and the optical axis is orthogonal to the sub scanning section The direction to be taken is the z axis, and can be expressed by the following continuous function.

  Scan start side

  End of scanning

(r 'is the sub-scanning direction of curvature _{radius, D 2, D 4, D} 6, D 8, D 10 coefficients)
The coefficient suffix s represents the scanning start side, and e represents the scanning end side.

  Here, the radius of curvature in the sub-scanning direction is a radius of curvature in a cross section orthogonal to the shape (bus line) in the main scanning direction.

Table 1 shows various numerical values of the image forming apparatus of Example 1 of the present invention. Here, “E−x” indicates “10 ^−x ”. The surface R1 is the entrance surface of the first imaging lens 6a _1, the R2 surface emitting surface of the first imaging lens 6a _1, R3 face the incident surface of the second imaging lens 6b _1, the R4 Face of 2 is a exit surface of the imaging lens 6b _1. The same applies to Tables 2 and 3 described later.

As shown in FIG. 1, the image forming apparatus according to the present embodiment includes a plurality of stations. Then, by separating the light beam in the sub-scanning direction on the facets of the polygon mirror, the light beam that has passed through the first imaging lens 6a ₁ (6a ₂ ) is easily separated and guided to different scanning surfaces. . Further, since the first imaging lens 6a ₁ (6a ₂ ) is shared by the two stations S1, S2 (S3, S4), the number of lenses can be reduced, and the entire apparatus can be simplified.

  In FIG. 3, (a1) represents the scanning line curve of the scanning line on the scanned surface 8a when the reflecting surface of the scanning line curvature correcting mirror 9a of the present embodiment is bent in a convex shape in the longitudinal direction. In FIG. 4, (b1) represents the scanning line curvature of the scanning line on the scanned surface 8a when the reflecting surface of the scanning line curvature correcting mirror 9a of the present embodiment is bent in a concave shape in the longitudinal direction. In FIGS. 3 and 4, (a1) and (b1), reference numeral 901 denotes a scanning line (scanning line curve) on the scanned surface 8a.

  FIG. 3 shows that the scanning line 901 becomes the scanning line 901a when the reflecting surface is bent into a convex shape. FIG. 4 shows that the scanning line 901 becomes the scanning line 901a when the reflecting surface is bent into a concave shape.

  As shown in the schematic diagrams of FIGS. 3 and 4, when the scanning line curvature correcting mirror 9a is bent, the light beam (light beam) traveling toward the scanned surface 8a is continuously subdivided from the image center toward the image edge. The surface to be scanned is scanned so as to be separated in the scanning direction (z direction on the surface to be scanned). That is, it is possible to generate (correct) the scanning line curvature.

  When the reflecting surface of the scanning line curvature correcting mirror 9a is bent into a convex shape as shown in FIG. 3, the scanning line 901 can be corrected to the scanning line 901a, and the scanning line curvature can be corrected to the plus side in the sub-scanning direction. Conversely, when the reflecting surface is bent into a concave shape, the scanning line 901 can be corrected to the scanning line 901a and the scanning line curve can be corrected to the minus side in the sub-scanning direction as shown in FIG.

  Also, as shown in FIG. 3, when the reflecting surface of the scanning line curvature correcting mirror 9a is bent into a convex shape, the image changes longer in the positive direction in the main scanning direction and the magnification becomes longer. Conversely, when the reflecting surface is bent into a concave shape as shown in FIG. 4, the image changes in the minus direction and the magnification is shortened.

  FIG. 5 is a schematic diagram showing correction of scanning line curvature according to the first embodiment of the present invention. In FIG. 5, only the scanning line curvature correcting mirror 9a and the photosensitive drum 8a are shown. Other imaging optical elements are omitted for convenience of explanation.

  In FIG. 5, a scanning light beam 401 indicates a light beam toward the center of the photosensitive drum surface 8a, and scanning light beams 402 and 403 indicate a light beam toward the end of the photosensitive drum surface 8a. The scanning line curvature correcting mirror 9a is formed so that the reflecting surface (mirror surface) 9a1 bends in the generatrix direction (longitudinal direction) by a mechanical member as an adjusting means (not shown).

  FIG. 5 shows a state in which the reflecting surface of the scanning line curve correcting mirror 9a is bent into a convex shape, and the scanning line curve 901 is corrected to the scanning line 901a in the plus direction and the overall magnification in the main scanning direction is long. The direction is changed.

  In the initial state, the scanning line curvature correcting mirror 9a is held in the shape indicated by the solid line (the bus line is a straight line), and the scanning line 901 in this state is curved to the negative side as indicated by the solid line. The scanning line bending caused by the error of the imaging optical element is measured at the time of initial adjustment, and the scanning line is corrected so as to be a linear scanning line 901a. The shape of the reflection surface of the scanning line curvature correcting mirror 9a at the time of correction is bent in a bus-line convex shape by a mechanical member (not shown) as shown by a broken line, and the amount of bending so that the amount of bending of the scanning line 901a is reduced ( Adjust the adjustment amount.

  In this embodiment, the light beam incident angle α = 49.37 (deg) to the scanning line curvature correcting mirrors 9a, 9d, and the light beam incident angle α = 42.75 (deg) to the scanning line curvature correcting mirror mirrors 9c, 9f. The distance to the surface to be scanned is 155.5 (mm) in all cases.

  In this embodiment, the reflecting surfaces of the scanning line curvature correcting mirrors 9a and 9d are bent into a convex shape, and the reflecting surfaces of the scanning line curvature correcting mirrors 9c and 9f are bent into a concave shape by a second adjusting means (not shown). Scan line curvature is corrected to reduce color misregistration in the sub-scanning direction. At the same time, the overall magnification (image length) (scanning line length) in the main scanning direction is adjusted by the folding mirrors 9b and 9e, and color misregistration is also reduced in the main scanning direction.

  Bending mirrors 9b and 9e for adjusting the overall magnification in the main scanning direction by a first adjusting means (not shown) are mirrors having the smallest incident angle of the light beam in stations S1, S2, S3, and S4. The mirrors 9b and 9e are hereinafter referred to as “second reflecting mirror” or “overall magnification adjusting mirror”.

  The incident angle α of the light beam to the overall magnification adjusting mirrors 9b and 9e is α = 4.3 (deg).

  The overall magnification adjusting mirror 9b of the station S2 and the overall magnification adjusting mirror 9e of the station S4 have the same shape.

  In the present embodiment, the overall magnification adjustment mirrors 9b and 9e in the main scanning direction are mirrors closest to the optical deflector 5, and are configured to have high overall magnification adjustment sensitivity.

  The overall magnification sensitivity (M1, M2) is an adjustment amount (deflection amount) of the optical element as shown in FIGS. 7B, 8B, and 9B (inclination of the graph) described later. ) It is defined as the overall magnification fluctuation per 1 μm (mm). Further, the scanning line curvature sensitivity (V1, V2) described later is the adjustment amount of the optical element (as shown in FIG. 7A, FIG. 8A, FIG. 9A (gradient of the graph) described later). (Deflection amount) It is defined as the amount of scan line curve variation (mm) per 1 μm.

In general, to change the overall magnification,
(1) Increase the distance r between the mirror and the surface to be scanned.
(2) Increase the mirror deflection amount δZ.
It is necessary.

  In the present embodiment, the scanning line curvature correcting mirrors 9c and 9f are used for the scanning line curvature correction so that the overall magnification of all stations can be changed with the smallest possible curvature amount and the overall magnification error can be reduced.

  In this example, the bending mirrors 9a, 9c, 9d, and 9f were selected to correct the scanning line curvature because the light beam incident angle in the sub-scanning section was large, the scanning line curvature sensitivity was high, and the mirror ( This is because the amount of bending of the reflecting surface can be reduced. There is a problem that when the amount of bending of the mirror increases, the mechanical mechanism for adjustment becomes complicated.

  The reason why the overall magnification adjustment mirrors 9b and 9e are used for the overall magnification correction is that they are farthest from the scanned surface 8, the light incident angle on the mirror is small, the scanning line curvature sensitivity is low, and the mirror This is because the generation amount of the scanning line curve is small even if the angle is bent.

In this embodiment, the scanning line curvature sensitivities of the scanning line curvature correction mirror (first reflection mirror) and the overall magnification adjustment mirror (second reflection mirror) are V1 and V2, respectively. Also, let M1 and M2 be the overall magnification sensitivities of the scanning line curvature correction mirror (first reflection mirror) and the overall magnification adjustment mirror (second reflection mirror). then,
V2 / V1 ≦ 0.5 (1)
M2 / M1 ≧ 0.7 (2)
Is set to satisfy the following conditions.

  In this embodiment, the overall magnification sensitivity M2 that changes when the overall magnification adjusting mirror (second reflection mirror) 9b is bent and the scanning line curvature correcting mirror (first reflection mirror) 9c are bent. The ratio of the changing overall magnification sensitivity M1 is set to 6: 5.

That is, M2 / M1 = 1.2
This satisfies the conditional expression (2).

  Further, the scanning line curve sensitivity V2 that changes when the overall magnification adjusting mirror (second reflection mirror) 9b is bent and the scan line curve correction mirror (first reflection mirror) 9c that change when the mirror is bent are changed. The ratio of the scanning line curvature sensitivity V1 is set to 3: 250.

That is, V2 / V1 = 0.012.
This satisfies the conditional expression (1).

  If these conditional expressions (1) and (2) are not satisfied, it is not possible because both the color misregistration in the sub-scanning direction and the color misregistration in the main scanning direction cannot be reduced at the same time while maintaining the optical performance.

  The scan line curve of the scan line before adjustment in this embodiment is shown in FIG.

  In order to reduce the scanning line curvature of the scanning lines of this embodiment, the reflecting surfaces of the scanning line curvature correcting mirrors 9c and 9f of the stations S2 and S4 are convex, and the scanning line curvature correcting mirror 9a of the stations S1 and S3. Therefore, it is necessary to bend the reflecting surface of 9d into a concave shape. In this case, the overall magnification of the stations S2 and S4 changes in reverse between the stations with respect to the overall magnification (image length) of the stations S1 and S3 in the main scanning direction. However, in the present embodiment, the overall magnification adjustment mirrors 9b and 9e provided in the stations S2 and S4 and the reflection surfaces of the scanning line curvature correction mirrors 9c and 9f are bent into a concave shape, so that The magnification error is aligned with the stations S1 and S3.

  That is, in this embodiment, the overall magnification error of the other scanned surface is adjusted based on the overall magnification error of one scanned surface.

  Next, the relationship between the amount of bending of the bending mirror of this embodiment, the amount of bending and the amount of change in the overall magnification is shown in FIGS.

  In each figure, (a) shows the bending change amount, and (b) shows the overall magnification change amount. 7 shows scanning line curvature correcting mirrors 9a and 9d, FIG. 8 shows overall magnification adjusting mirrors 9b and 9e, and FIG. 9 shows the amount of change in scanning line curvature correcting mirrors 9c and 9f.

  In the scanning line curvature correcting mirrors 9a, 9c, 9d, and 9f of the present embodiment, the incident angles of the light beams are set as described above. The scanning line curvature correcting mirrors 9a and 9d have the same configuration, the luminous flux incident angle is 49.37 (deg) (FIG. 7), and the overall magnification adjusting mirrors 9b and 9e have the same configuration. The incident angle is 4.3 (deg) (FIG. 8). Further, the scanning line curvature correcting mirrors 9c and 9f have the same configuration, and the light beam incident angle is 42.75 (deg) (FIG. 9).

  In this embodiment, the optical elements are arranged so that the incident angle α of the light beam incident on the scanning line curvature correcting mirrors 9a, 9c, 9d, and 9f is 15 (deg) or more (the folding angle is 80 (deg) or more). is doing. When the incident angle α is 40 (deg) or less, the bending sensitivity becomes low, which is not good.

  7, 8, and 9, the horizontal axis indicates the deflection amount (adjustment amount) (μm) of the mirror in the vicinity of the most off-axis light beam (Y = 90 (mm)), and the vertical axis indicates the scanning line. The bending change amount (mm) and the overall magnification change amount (mm) are shown.

  In each figure, the slope indicates the sensitivity of the scanning line curve and the sensitivity of the overall magnification change.

  The amount of bending in this embodiment is defined by the difference in the arrival position of the most off-axis light beam and the on-axis light beam on the photosensitive drum surface in the sub-scanning direction (rotating direction of the photosensitive drum).

  The scanning line curvature correction mirrors 9a, 9c, 9d, and 9f have a distance S of 164.0 (mm) from the optical deflector 5 as described above, and the overall magnification adjustment mirrors 9b and 9e have a distance S from the optical deflector 5. Is 117.3 (mm).

  The scanning line curvature correcting mirrors 9a, 9c, 9d, and 9f have the same distance from the optical deflector 5, but the scanning line curvature correcting mirrors 9a and 9c and the scanning line curvature correcting mirrors 9d and 9f are the same. 7 and 9, it can be seen that the adjustment sensitivity of the bending is different.

  In the present embodiment, the measured value of the bending of the stations S1 and S3 is 0.06 (mm). Therefore, the scanning line curvature correcting mirrors 9a and 9d are not curved in the sub-scanning direction by bending the bus bar in the normal direction of the mirror surface by 63 (μm) at the position of Y = 90 (mm). A scan line is obtained.

  Next, the overall magnification is corrected.

  In this embodiment, since the bend of 0.06 (mm) is changed at the stations S1 and S3, the overall magnification is changed by 0.66 (mm) from FIG. 7 (b). In order to correct this overall magnification deviation, the overall magnification adjusting mirrors 9b and 9e are bent by 45.4 (μm).

  In this embodiment, only the overall magnification that changes due to the deflection of the mirror is corrected, but the overall magnification error that occurs due to an assembly error or the like may also be corrected.

  Next, how to deflect the scanning line curvature correcting mirror of this embodiment will be described.

  The scanning line curvature correcting mirror of the present embodiment has a configuration in which the reflecting surface is bent in both a concave shape and a convex shape, the amount of bending of the mirror can be reduced, and the bending of all four stations S1 to S4 can be reduced. The direction can be made close to the design value (straight line).

  The procedure for adjusting the scanning line bending and the overall magnification is as follows.

(1) Measure the scanning line curvature of all stations S1 and S2 and stations S3 and S4 at the time of shipment using a CCD camera, etc.
(2) Calculate the bending amount of each station of stations S1 to S4.
(3) The amount of bending is converted into the correction amount of the scanning line curvature correcting mirror using the relationship shown in FIGS.
(4) Bending the scanning line curvature correcting mirrors 9a, 9c, 9d, 9f using a mechanical member such as a screw,
(5) Measure the overall magnification of stations S1 and S2 and stations S3 and S4.
(6) Calculate the difference between the overall magnification of stations S1 and S2 and stations S3 and S4.
(7) Based on the difference of the overall magnification, it is converted into the overall magnification adjustment amount using the table shown in FIG.
(8) The overall magnification adjusting mirrors 9b and 9e are bent using a mechanical member such as a screw.

  Through the above flow, the station S2 bends the overall magnification adjusting mirror 9b so as to match the overall magnification error of the station S1 after the bending adjustment. Similarly, the station S4 bends the overall magnification adjusting mirror 9e so as to meet the overall magnification error of the station S3 after the bending adjustment.

  In this way, the bending direction and the bending amount of all four stations on the photosensitive drum surface are made to coincide with each other, the overall field error in the main scanning direction is reduced, and the color shift is reduced in both the main scanning direction and the sub-scanning direction. Can do.

  In this embodiment, since the stations S1 and S3 have the same optical configuration, the overall magnification errors of the stations S1 and S3 are almost the same, and the overall magnification errors of the stations S1 to S4 can be made to match. However, if the overall magnification errors of the stations S1 and S3 are significantly different, it is desirable to select a combination having substantially the same overall magnification error by changing the pair of the stations S3 and S4 combined with the stations S1 and S2.

  In addition, the imaging optical system of the present embodiment is composed of a plastic lens having a light-transmitting power at the optical element closest to the scanning surface, and a sealing member such as dustproof glass is provided by sealing the light emission direction. It is possible to prevent toner or the like from entering the optical box without using it. The optical element having light transmitting power may be made of glass, and may be a diffractive optical element having diffractive power.

  As described above, in this embodiment, by configuring the image forming apparatus using a plurality of optical scanning devices (stations) having the above-described configuration, it is possible to reduce the amount of bending and the overall magnification error on the surface of the photosensitive drum. it can. As a result, color misregistration can be reduced in both the sub-scanning direction and the main scanning direction. Furthermore, it is possible to achieve an image forming apparatus that can reduce the size of the entire apparatus.

  FIG. 10 is a sectional view (sub-scanning sectional view) of the principal part in the sub-scanning direction in the second embodiment of the optical scanning device of the present invention. 10, the same elements as those shown in FIGS. 1 and 2 are denoted by the same reference numerals.

This embodiment differs from the first embodiment described above in that the first and second imaging lenses 6a (6a ₁ , 6a ₂ ) and 6b (6b ₁ , 6b ₂ , 6b) constituting the imaging optical systems LB1 to LB4. ₃ , 6b ₄ ) with different surface shapes. Further, in order to scan the four stations S1 to S4 with the single optical deflector 5, the scanning line curvature correcting mirrors 9a, 9c, 9e and 9f are connected to the second imaging lens 6b (6b ₁ , 6b ₂ , 6b ₃ , 6b ₄ ) and the scanned surface 8 (8a, 8b, 8c, 8d). Other configurations and optical actions are the same as those in the first embodiment, and the same effects are obtained.

That scanning line curvature correction mirror 9a for the present embodiment to scan a single optical deflector 5 in the fourth station S1~S4, 9c, 9e, the 9f second imaging lens 6b (6b _1, 6b ₂ , 6b ₃ , 6b ₄ ) and the scanned surface 8 (8a, 8b, 8c, 8d). The incident optical system is a so-called oblique incidence in which a light beam incident on the deflecting surfaces 5a1 and 5b1 of a single optical deflector 5 is incident at a predetermined angle β (2.2 deg) from an oblique direction in the sub-scan section. It consists of an optical system.

In FIG. 10, LB1 is an imaging optical system of the station S1, and has a first imaging lens 6a ₁ and a second imaging lens 6b ₁ made of a plastic material. LB2 is an imaging optical system of the station S2, and has a first imaging lens 6a ₁ and a second imaging lens 6b ₂ made of a plastic material. LB3 is an imaging optical system of the station S3, and a first imaging lens 6a ₂ and the second imaging lens 6b ₃ made of plastic material. LB4 is an imaging optical system of the station S4, has a first imaging lens 6a ₂ made of plastic material and the second imaging lens 6b _4.

The first imaging lens 6a ₁ is shared by the stations S1 and S2, and the first imaging lens 6a ₂ is shared by the stations S3 and S4.

  Both the first and second imaging lenses 6a and 6b are formed of anamorphic lenses having an aspheric shape in the main scanning section. The imaging optical systems LB1 to LB4 each form a light beam based on the image information deflected and scanned by the optical deflector 5 on the photosensitive drum surface 8 (8a, 8b, 8c, 8d) as a scanned surface. In addition, the imaging optical systems LB1 to LB4 each have a conjugate relationship between the deflection surfaces 5a1 and 5b1 of the optical deflector 5 and the photosensitive drum surface 8 (8a, 8b, 8c, 8d) in the sub-scan section. Has a tilt correction function.

  10 (10a, 10b, 10c, 10d) is a dust-proof glass, and is composed of parallel plates. The dust-proof glass 10 is used to seal the exit when the light beam is emitted from the optical scanning device, and is disposed at an inclination of 5 deg in the sub-scanning section in order to prevent the regular reflection light from returning to the light source means. .

  Table 2 shows various values of the image forming apparatus of Example 2 of the present invention.

  In this embodiment, the optical axes of the first and second imaging lenses 6a and 6b are both arranged parallel to the normal lines of the deflecting surfaces 5a1 and 5b1 of the optical deflector 5. Furthermore, the optical axes of the first and second imaging lenses 6a and 6b are both −0.5 (mm) and 1.456 (mm) in the sub-scanning direction in order from the point where the incident light beam intersects the deflecting surfaces 5a1 and 5b1. It is configured to be shifted so that only the height is different. Thus, in this embodiment, the deterioration of the wavefront aberration due to the oblique incidence is reduced, and the scanning line curve amount on the scanned surface 8 is reduced.

  In the present embodiment, the optical axes of the first and second imaging lenses 6a and 6b are both shifted. However, the present invention is not limited to this. For example, the same effect can be obtained by tilting. Further, the same effect can be obtained by shifting or / and tilting only the exit surface r4 of the second imaging lens 6b.

  In this embodiment, as shown in FIG. 10, the light beam from the light source means 1 is incident on the deflecting surfaces 5a1 and 5b1 with a predetermined angle. Accordingly, as shown in FIG. 10, a plurality of light beams can be bent by the mirrors 9b and 9d and guided to the plurality of photosensitive drum surfaces 8a, 8b, 8c and 8d. Further, since the light beam incident on the deflecting surfaces 5a1 and 5b1 is incident at a predetermined angle from the oblique direction in the sub-scan section, the on-axis light beam and the off-axis light beam pass through the imaging optical systems LB1 to LB4. The height in the sub-scanning direction (height from the optical axis) is different from each other.

  In this embodiment, the bending adjustment is performed by the scanning line curvature correcting mirrors 9a, 9c, 9e, and 9f, and the overall magnification adjustment is performed by the overall magnification adjusting mirrors 9b and 9d. It is configured to bend in both shapes.

  FIG. 11 shows the scanning line curve on the surface to be scanned before adjustment in this embodiment.

  In a state where the scanning line curvature correction is not performed, as shown by scanning lines 701 to 704, the scanning line bending direction is the plus (+) direction for stations S1 and S2, and the minus (−) direction for S3 and S4.

  In this embodiment, since the scanning lines 701 to 704 are curved by the scanning line curvature correcting mirrors 9a, 9c, 9e, and 9f of the stations S1 to S4, the reflecting surfaces of the scanning line curvature correcting mirrors 9a and 9f are convex. The mirrors 9c and 9e for correcting the shape and scanning line curvature are bent in a concave shape. At this time, the overall magnification in the main scanning direction changes in the direction in which the stations S1 and S4 become longer (plus direction) and in the direction in which the stations S2 and S3 become shorter (minus direction).

  The scanning line curvature is corrected as described above.

  Next, in order to reduce the overall magnification error in the main scanning direction, the reflecting surfaces of the overall magnification adjustment mirrors 9b and 9d are curved in a convex shape so that the overall magnification of the stations S2 and S3 becomes longer (plus direction). to correct. In this way, it is possible to simultaneously correct color misregistration in the sub-scanning direction and the main scanning direction and provide a high-definition color image forming apparatus.

In this embodiment, the amount of warpage in the sub-scanning direction of the imaging lenses 6b ₁ and 6b ₄ is controlled so that the overall magnification errors of the stations S1 and S4 are in the same direction.

  In the present embodiment, the ratio of the overall magnification sensitivity M2 that changes when the overall magnification adjusting mirror 9b is bent and the overall magnification sensitivity M1 that changes when the scanning line curvature correcting mirror mirror 9c is bent is 37. : Set to 50.

That is, M2 / M1 = 0.74
This satisfies the conditional expression (2).

  Further, the ratio of the scanning line curvature sensitivity V2 that changes when the overall magnification adjusting mirror 9b is deflected to the scanning line curvature sensitivity V1 that changes when the scanning line curvature correction mirror 9c is deflected is 1: 5. It is set to become.

That is, V2 / V1 = 0.2
This satisfies the conditional expression (1).

  Next, FIG. 12, FIG. 13, and FIG. 14 show the relationship between the amount of bending and the amount of bending of the bending mirror of this embodiment, and the amount of change in overall magnification.

  In each figure, (a) shows the bending change amount, and (b) shows the overall magnification change amount. 12 shows the scanning line curvature correcting mirrors 9a and 9f, FIG. 13 shows the overall magnification adjusting mirrors 9b and 9d, and FIG. 14 shows the amount of change of the scanning line curvature correcting mirrors 9c and 9e.

  In the scanning line curvature correcting mirrors 9a, 9c, 9e, and 9f of this embodiment, the incident angles of the light beams are set as described above. The scanning line curvature correcting mirrors 9a and 9f have the same configuration, the luminous flux incident angle is 45.2 (deg) (FIG. 12), and the overall magnification adjusting mirrors 9b and 9d have the same configuration. The incident angle is 22.8 (deg) (FIG. 13). Further, the scanning line curvature correcting mirrors 9c and 9e have the same configuration, and the light beam incident angle is 22.4 (deg) (FIG. 14).

  In this embodiment, the optical elements are arranged so that the incident angle α of the light beam incident on the scanning line curvature correcting mirrors 9a, 9c, 9e, 9f is 20 (deg) or more (the folding angle is 80 (deg) or more). ing. When the incident angle α is 40 (deg) or less, the bending sensitivity becomes low, which is not good.

  12, 13, and 14, the horizontal axis indicates the amount of deflection (adjustment amount) (μm) of the mirror in the vicinity of the fulcrum of the mirror (Y = 50 (mm)), and the vertical axis indicates the bending change of the scanning line. The amount (mm) and the total magnification change (mm) are shown. In each figure, the slope indicates the sensitivity of the scanning line curve and the sensitivity of the overall magnification change.

  In the present embodiment, the Y-coordinates of the most off-axis light beam passing positions are 67 (mm), 37.3 (mm), and 54.7 (mm), respectively.

  The amount of bending in this embodiment is defined by the difference in the arrival position of the most off-axis light beam and the on-axis light beam on the photosensitive drum surface in the sub-scanning direction (rotating direction of the photosensitive drum).

  As described above, the scanning line curvature correcting mirrors 9a and 9f have a distance S of 103 (mm) from the optical deflector 5, and the scanning line curvature correcting mirrors 9c and 9e are 82.2 (mm). The overall magnification adjusting mirrors 9b and 9d have a distance S of 53.2 (mm) from the optical deflector 5.

  In the present embodiment, the measured value of the bending of the stations S1 and S4 is 0.03 (mm). Accordingly, the scanning line curvature correcting mirrors 9a and 9f are not curved in the sub-scanning direction by bending the bus line in the surface normal direction of the mirror by 5.5 (μm) at the position of Y = 50 (mm). A linear scan line is obtained.

  Next, the overall magnification is corrected.

  In this embodiment, since the bend of 0.03 (mm) is changed at the stations S1 and S3, the overall magnification is changed by 0.094 (mm) from FIG. 12 (b). In order to correct this overall magnification shift, the overall magnification adjusting mirrors 9b and 9d are bent by 5.8 (μm) by the adjusting means.

  In this embodiment, if the mirror for adjusting the overall magnification is bent, not only the overall magnification but also the bending changes, but the mirrors for adjusting the overall magnification 9b and 9d are bent by 5.8 (μm) as shown in FIG. There is no problem because the bend only changes by 3.2 (μm).

  Further, in this embodiment, only the overall magnification that changes due to the deflection of the scanning line curvature correcting mirror is corrected, but other overall magnification errors caused by assembly errors and the like may be corrected together.

  As described above, even in an optical scanning device that scans four drum surfaces using a single optical deflector, it is possible to provide a color image forming apparatus with little color misregistration in both the main scanning direction and the sub-scanning direction.

  FIG. 15 is a sectional view (sub-scanning sectional view) of the main part in the sub-scanning direction of Embodiment 3 of the present invention.

  This embodiment is different from the second embodiment described above in that the overall magnification adjusting mirrors 9a, 9c, 9e, and 9g for correcting the overall magnification are arranged in the stations S1 to S4. Other configurations and optical actions are the same as those in the second embodiment, and the same effects are obtained.

That is, in this embodiment, the overall magnification adjusting mirrors 9a, 9c, 9e, and 9g are used as the first imaging lens 6a (6a ₁ and 6a ₂ ) and the second imaging in the stations S1, S2, S3, and S4. It is provided in the optical path between the lenses 6b (6b ₁ , 6b ₂ , 6b ₃ , 6b ₄ ).

  In the figure, 9a and 9b are bending mirrors arranged at the station S1, and 9c and 9d are bending mirrors arranged at the station S2. Further, 9e and 9f are bending mirrors arranged in the station S3, and 9g and 9h are bending mirrors arranged in the station S4. These bending mirrors 9a to 9h are arranged in the optical path from the optical deflector 5 (5a, 5b) to the scanned surface 8 (8a, 8b, 8c, 8d).

  The image forming apparatus according to the present embodiment includes four optical scanning devices (stations) S1, S2, S3, and S4 that use the optical deflector 5 in common. The optical deflector 5 scans the photosensitive drum surfaces 8a, 8b, 8c and 8d as different scan surfaces, and forms a color image by multiple development.

  In the present embodiment, the number of folding mirrors is larger than that in the second embodiment, thereby further reducing the size and thickness of the second embodiment.

  In this embodiment, in each station S1, S2, S3, S4, the reflecting means of each folding mirror 9a, 9b, 9c, 9d, 9e, 9f, 9g, 9h is configured to bend in the longitudinal direction by the adjusting means. . In this embodiment, the bending in the sub-scanning direction (scanning line bending) of the scanning lines on the scanned surfaces 8a, 8b, 8c, and 8d is corrected by the bending mirrors 9b, 9d, 9f, and 9h. Hereinafter, the bending mirrors 9b, 9d, 9f, and 9h are referred to as a first reflecting mirror or a scanning line curvature correcting mirror. Further, the overall magnification of the scanned surface is corrected by the bending mirrors 9a, 9c, 9e, and 9g. Hereinafter, the bending mirrors 9a, 9c, 9e, and 9g are referred to as a second reflecting mirror or an overall magnification adjusting mirror.

  Table 3 shows various numerical values of the image forming apparatus of Example 3 of the present invention.

Table 3
In this embodiment, the light beam incident angle α = 29.1 (deg) to the overall magnification adjusting mirror 9a and the light beam incident angle α = 18.0 (deg) to the scanning line curvature correcting mirror 9b are configured. Further, the light beam incident angle α = 17.5 (deg) to the overall magnification adjusting mirror 9c and the light beam incident angle α = 25.5 (deg) to the scanning line curvature correcting mirror 9d are configured. Further, the light beam incident angle α = 18.2 (deg) to the overall magnification adjusting mirror 9e and the light beam incident angle α = 29.0 (deg) to the scanning line curvature correcting mirror 9f are configured. Further, the light beam incident angle α = 26.1 (deg) to the overall magnification adjusting mirror 9g and the light beam incident angle α = 16.9 (deg) to the scanning line curvature correcting mirror 9h are configured.

  Further, the mirror for adjusting the overall magnification in the main scanning direction is the mirror closest to the optical deflector 5 and is farthest from the surface to be scanned so that the overall magnification errors of all the stations S1 to S4 can be aligned with the smallest possible amount of curvature. The overall magnification is adjusted by the bending mirrors 9a, 9c, 9e, and 9g.

  In the present embodiment, since the mirror for correcting the overall magnification is arranged in the optical path of all the stations S1 to S4, the overall magnification difference between the four stations can be further reduced as compared with the first and second embodiments.

  FIG. 16 shows the scan line curve before the scan line curve correction of this embodiment.

  In this embodiment, in order to correct the scanning line curvature to 0, the reflecting surface of the scanning line curvature correcting mirror 9b is curved into a convex shape, and the reflecting surfaces of the scanning line curvature correcting mirrors 9d, 9f, 9h are curved into a concave shape. ing. Then, the overall magnification changed by the scanning line curve adjustment by the adjusting means is obtained by curving the reflection surface of the overall magnification adjustment mirror 9a into a concave shape and the reflection surfaces of the overall magnification adjustment mirrors 9c, 9e, 9g into a convex shape. It is corrected.

  In the present embodiment, the ratio of the overall magnification sensitivity M2 that changes when the overall magnification adjusting mirror 9a is bent and the overall magnification sensitivity M1 that changes when the scanning line curvature correcting mirror 9b is bent is 21: It is set to be 25.

That is, M2 / M1 = 0.84
This satisfies the conditional expression (2).

  Further, the ratio of the scanning line curvature sensitivity V2 that changes when the overall magnification adjusting mirror 9a is deflected to the scanning line curvature sensitivity V1 that changes when the scanning line curvature correction mirror 9b is deflected is 12:25. It is set to become.

That is, V2 / V1 = 0.48
This satisfies the conditional expression (1).

  The station S4 is the same as the station S1.

  The ratio of the overall magnification M2 that changes when the overall magnification adjusting mirror 9c is bent and the overall magnification M1 that changes when the scanning line curvature correcting mirror 9d is bent is set to 39:50. ing.

That is, M2 / M1 = 0.78
This satisfies the conditional expression (2).

  Further, the ratio of the scanning line curve V2 that changes when the overall magnification adjusting mirror 9c is bent and the scanning line curve V1 that changes when the scanning line curve correcting mirror 9d is bent is 1:20. It is set.

That is, V2 / V1 = 0.05
This satisfies the conditional expression (1).

  The station S3 is the same as the station S2.

  Next, FIG. 17, FIG. 18, FIG. 19, and FIG. 20 show the relationship between the amount of bending of the bending mirror of this embodiment, the amount of bending, and the amount of change in overall magnification.

  In each figure, (a) shows the bending change amount, and (b) shows the overall magnification change amount. 17 is an overall magnification adjustment mirror 9a, 9g, FIG. 18 is a scanning line curve correction mirror 9b, 9h, FIG. 19 is an overall magnification adjustment mirror 9c, 9e, and FIG. 20 is a scan line curve correction mirror 9d. The amount of change of 9f is shown.

  In this embodiment, scanning line bending is performed by the scanning line bending correction mirrors 9b, 9d, 9f, and 9h, and overall magnification correction is performed by the overall magnification adjustment mirrors 9a, 9c, 9e, and 9g.

  As described above, the scanning line curvature correction mirror and the overall magnification adjustment mirror are provided at all stations, so that the overall magnification error in the main scanning direction can be corrected with higher precision. A color image forming apparatus with little deviation can be provided.

  Next, a fourth embodiment of the present invention will be described. The optical scanning device of this embodiment is the same as that shown in the first to third embodiments.

This embodiment is different from the above-described embodiments in that the second imaging lens 6b (6b ₁ , 6b ₂ , 6b ₃ , 6b ₄₎ is a part constituting the second optical means by an adjusting means (not shown). ) Is rotated (eccentric) about the Y axis (main scanning direction) to adjust the scanning line curvature. Other configurations and optical actions are the same as those in the first embodiment, and the same effects are obtained.

In the present embodiment, the overall magnification adjustment is performed by the overall magnification adjustment mirrors 9b and 9e having the smallest incident angle of the light beam, as in the first embodiment. When the scanning line curve is performed by rotating the second imaging lens 6b (6b ₁ , 6b ₂ , 6b ₃ , 6b ₄ ) around the Y axis as in the present embodiment, the overall magnification can be reduced by adjusting the scanning line curve. Fluctuation can be prevented. In addition, the adjustment amount of the overall magnification can be reduced, and the adjustment accuracy of the overall magnification can be improved.

The scanning line curvature sensitivity V and the overall magnification sensitivity M of the present embodiment are determined by scanning the rotation amount per minute around the Y axis of the second imaging lens 6b (6b ₁ , 6b ₂ , 6b ₃ , 6b ₄ ). Defined by the amount of movement of the line curvature,
V = 0.0013mm / min,
M = 0.0003 mm / min.

For example, in order to correct the scanning line curvature by 20 μm, the second imaging lens 6b (6b ₁ , 6b ₂ , 6b ₃ , 6b ₄ ) may be rotated around the Y axis for 15 minutes. The total magnification error occurring at that time is 0.0046 mm. As a result, it is possible to reduce the overall magnification error that occurs in the scanning line curve adjustment.

In the present embodiment, the scan line curve and the second imaging lens _{6b (6b 1, 6b 2,} 6b 3, 6b 4) adjusted by rotating about the Y axis, the second imaging lens _{6b (6b 1, 6b 2,} 6b 3, 6b 4) similarly to the flexed in the sub-scanning direction (Z direction) of the effect is obtained.

As described above, by performing the scan line curve in the second imaging lens _{6b (6b 1, 6b 2,} 6b 3, 6b 4), can reduce the overall magnification correction amount, the entire magnification error in the main scanning direction Correction can be made with higher definition. Thereby, a color image forming apparatus with little color misregistration in both the main scanning direction and the sub-scanning direction can be provided.
[Color image forming device]
FIG. 21 is a sub-scan sectional view of the color image forming apparatus of the present invention.

  In the figure, 60 is a color image forming apparatus, 11 is an image forming apparatus having any of the configurations shown in the first to third embodiments, 21, 22, 23, and 24 are photosensitive drums as image carriers, Reference numerals 32, 33, and 34 denote developing devices. Reference numeral 51 denotes a conveyance belt, 52 denotes an external device such as a personal computer, and 53 denotes a printer controller that converts color signals input from the external device 52 into image data of different colors and inputs them to the image forming apparatus 11.

  In the figure, the color image forming apparatus 60 receives R (red), G (green), and B (blue) color signals from an external device 52 such as a personal computer. These color signals are converted into C (cyan), M (magenta), Y (yellow), and B (black) image data (dot data) by a printer controller 53 in the apparatus. These image data are input to the image forming apparatus 11. The image forming apparatus 11 emits light beams (light beams) 41, 42, 43, and 44 that are modulated according to each image data, and the photosensitive surfaces of the photosensitive drums 21, 22, 23, and 24 are emitted by these light beams. Are scanned in the main scanning direction.

  The color image forming apparatus in this embodiment emits light beams corresponding to C (cyan), M (magenta), Y (yellow), and B (black) colors from one image forming apparatus 11. Then, image signals (image information) are recorded on the photosensitive drums 21, 22, 23, and 24, and a color image is printed at high speed.

  In the color image forming apparatus of this embodiment, as described above, the latent image of each color is formed on the corresponding photosensitive drums 21, 22, 23, and 24 using the light beams based on the respective image data by one image forming apparatus 11. Forming. After that, multiple transfer is performed on the recording material on the conveyance belt 51 to form one full-color image, and the full-color image is transferred to a sheet member (paper).

  As the external device 52, for example, a color image reading device including a CCD (line sensor) may be used. In this case, the color image reading apparatus and the color image forming apparatus 60 constitute a color digital copying machine.

Sub-scan sectional view of Embodiment 1 of the present invention The figure which shows the main scanning cross section of Example 1 of this invention Schematic diagram illustrating the principle of generation of scanning line bending according to the first embodiment of the present invention. Schematic diagram illustrating the principle of generation of scanning line bending according to the first embodiment of the present invention. Schematic diagram illustrating scanning line curvature correction according to the first embodiment of the present invention. Schematic diagram showing the scanning line curve of Example 1 of the present invention. The figure which shows the bending variation | change_quantity (a) and the whole magnification variation | change_quantity (b) of Example 1 of this invention. The figure which shows the bending variation | change_quantity (a) and the whole magnification variation | change_quantity (b) of Example 1 of this invention. The figure which shows the bending variation | change_quantity (a) and the whole magnification variation | change_quantity (b) of Example 1 of this invention. Sub-scan sectional view of Embodiment 2 of the present invention The figure which shows the bending variation | change_quantity (a) and the whole magnification variation | change_quantity (b) of Example 2 of this invention. The figure which shows the bending variation | change_quantity (a) and the whole magnification variation | change_quantity (b) of Example 2 of this invention. The figure which shows the bending variation | change_quantity (a) and the whole magnification variation | change_quantity (b) of Example 2 of this invention. The figure which shows the bending variation | change_quantity (a) and the whole magnification variation | change_quantity (b) of Example 2 of this invention. Sub-scan sectional view of Embodiment 3 of the present invention The figure which shows the scanning line curve of Example 3 of this invention. The figure which shows the bending variation | change_quantity (a) and the whole magnification variation | change_quantity (b) of Example 3 of this invention. The figure which shows the bending variation | change_quantity (a) and the whole magnification variation | change_quantity (b) of Example 3 of this invention. The figure which shows the bending variation | change_quantity (a) and the whole magnification variation | change_quantity (b) of Example 3 of this invention. The figure which shows the bending variation | change_quantity (a) and the whole magnification variation | change_quantity (b) of Example 3 of this invention. The figure which shows the image forming apparatus of this invention The figure which shows the conventional optical scanning device

Explanation of symbols

1 Light source means (semiconductor laser)
2 Light flux conversion element (collimator lens)
3 First cylindrical lens 4 Second cylindrical lens 7 Folding mirror 5 (5a, 5b) Deflection means (polygon mirror)
5a1,5b1 deflecting surface LB (LB1, LB2, LB3, LB4) imaging optical system 6a (6a _1, 6a ₂₎ first imaging lens _{6b (6b 1, 6b 2,} 6b 3, 6b 4) of the second Imaging lens 8 (8a, 8b, 8c, 8d) Scanned surface (photosensitive drum)
9a, 9b, 9c, 9d, 9e, 9f, 9g, 9h Bending mirror (reflection mirror)
S1, S2, S3, S4 station (optical scanning device)
M1, M2 Scanner 11 Image forming apparatus 21, 22, 23, 24 Image carrier (photosensitive drum)
31, 32, 33, 34 Developer 41, 42, 43, 44 Light beam 51 Conveying belt 52 External device 53 Printer controller 60 Color image forming device 61, 62, 63, 64 Station (optical scanning device)

Claims (10)

A plurality of light source means;
An incident optical system for guiding a plurality of light beams emitted from the plurality of light source means to a deflecting means;
An imaging optical system provided corresponding to each scanned surface for imaging a plurality of light beams deflected and scanned by the deflection surface of the deflecting unit on a plurality of corresponding scanned surfaces;
An optical scanning device comprising:
A plurality of reflection mirrors are arranged in at least one optical path between the deflecting means and the surface to be scanned, and the reflection of the first reflection mirror having the largest incident angle of the light beam among the plurality of reflection mirrors. Adjusting means for adjusting the scanning line curve by bending the surface, and adjusting means for adjusting the overall magnification by bending the reflecting surface of the second reflecting mirror having the smallest incident angle of the light beam among the plurality of reflecting mirrors. An optical scanning device characterized by the above. When the scanning line curvature sensitivity of the first and second reflecting mirrors is V1 and V2, respectively, and the overall magnification sensitivity of the first and second reflecting mirrors is M1 and M2,
V2 / V1 ≦ 0.5
M2 / M1 ≧ 0.7
The optical scanning device according to claim 1, wherein the following condition is satisfied. A plurality of light source means;
An incident optical system for guiding a plurality of light beams emitted from the plurality of light source means to a deflecting means;
An imaging optical system provided corresponding to each scanned surface for imaging a plurality of light beams deflected and scanned by the deflection surface of the deflecting unit on a plurality of corresponding scanned surfaces;
An optical scanning device comprising:
A plurality of reflecting mirrors are disposed in at least one optical path between the deflecting means and the surface to be scanned, and the reflecting surface of the reflecting mirror having the smallest incident angle of the light beam among the plurality of reflecting mirrors is arranged. First adjusting means for adjusting the overall magnification by bending, and second adjusting means for adjusting the scanning line curve by decentering a part of the imaging optical elements constituting the imaging optical system. An optical scanning device. A plurality of light source means;
An incident optical system for guiding a plurality of light beams emitted from the plurality of light source means to a deflecting means;
An imaging optical system provided corresponding to each scanned surface for imaging a plurality of light beams deflected and scanned by the deflection surface of the deflecting unit on a corresponding plurality of scanned surfaces;
An optical scanning device comprising:
A plurality of reflecting mirrors are arranged in at least one optical path between the deflecting means and the surface to be scanned, and the first reflecting mirror having the highest scanning line curvature sensitivity among the plurality of reflecting mirrors. Adjusting means for adjusting the scanning line curve by bending the reflecting surface; and adjusting means for adjusting the overall magnification by bending the reflecting surface of the second reflecting mirror having the smallest incident angle of the light beam among the plurality of reflecting mirrors; An optical scanning device comprising:   An image forming apparatus comprising: a plurality of image carriers that are arranged on a surface to be scanned of the optical scanning device according to claim 1 and that form images of different colors.   6. The image forming apparatus according to claim 5, further comprising a printer controller that converts color signals input from an external device into image data of different colors and inputs the image data to each optical scanning device. A plurality of light source means;
An incident optical system for guiding a plurality of light beams emitted from the plurality of light source means to a deflecting means;
An imaging optical system provided corresponding to each scanned surface for imaging a plurality of light beams deflected and scanned by the deflection surface of the deflecting unit on a plurality of corresponding scanned surfaces;
A method of adjusting an optical scanning device having:
A plurality of reflecting mirrors are disposed in at least one optical path between the deflecting means and the surface to be scanned, and the reflection of the first reflecting mirror having the largest incident angle of the light beam among the plurality of reflecting mirrors. An optical scanning device characterized in that the scanning line curve is adjusted by bending the surface, and the overall magnification is adjusted by bending the reflecting surface of the second reflecting mirror having the smallest incident angle of the luminous flux among the plurality of reflecting mirrors. Adjustment method. When the scanning line curvature sensitivity of the first and second reflecting mirrors is V1 and V2, respectively, and the overall magnification sensitivity of the first and second reflecting mirrors is M1 and M2,
V2 / V1 ≦ 0.5
M2 / M1 ≧ 0.7
The method of adjusting an optical scanning device according to claim 7, wherein the following condition is satisfied. A plurality of light source means;
An incident optical system for guiding a plurality of light beams emitted from the plurality of light source means to a deflecting means;
An imaging optical system provided corresponding to each scanned surface for imaging a plurality of light beams deflected and scanned by the deflection surface of the deflecting unit on a plurality of corresponding scanned surfaces;
A method of adjusting an optical scanning device having:
A plurality of reflecting mirrors are disposed in at least one optical path between the deflecting means and the surface to be scanned, and the reflecting surface of the reflecting mirror having the smallest incident angle of the light beam among the plurality of reflecting mirrors is arranged. A method of adjusting an optical scanning device, comprising: adjusting an overall magnification by bending and adjusting a scanning line curve by decentering a part of imaging optical elements constituting the imaging optical system. A plurality of light source means;
An incident optical system for guiding a plurality of light beams emitted from the plurality of light source means to a deflecting means;
An imaging optical system provided corresponding to each scanned surface for imaging a plurality of light beams deflected and scanned by the deflection surface of the deflecting unit on a plurality of corresponding scanned surfaces;
A method of adjusting an optical scanning device having:
A plurality of reflecting mirrors are arranged in at least one optical path between the deflecting means and the surface to be scanned, and the first reflecting mirror having the highest scanning line curvature sensitivity among the plurality of reflecting mirrors. The scanning line curve is adjusted by bending the reflecting surface, and the overall magnification is adjusted by bending the reflecting surface of the second reflecting mirror having the smallest incident angle of the light beam among the plurality of reflecting mirrors. Method for adjusting optical scanning device.