JP3836959B2 - Optical scanning device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical scanning device.
[0002]
[Prior art]
In connection with the color image forming apparatus, latent images are formed on each of the four photosensitive members by optical scanning, and the formed four electrostatic latent images are respectively developed with yellow, magenta, cyan, and black toners. There is known a system that obtains a color image by superimposing the obtained four color toner images on a recording medium on a sheet.
In such a color image forming system, it is known that the optical scanning of each photoconductor is performed separately by an optical scanning device provided for each photoconductor. Use is not cost effective.
A color image forming apparatus in which a rotating polygon mirror and an imaging optical system are shared for a plurality of photosensitive members is also known (JP-A-8-313833), but the imaging optical system is shared. As a result, bending occurs in the scanning line which is the “trajectory drawn by the light spot of each light beam on each photoconductor”. In order to correct and reduce this scanning line bending, in the invention described in the above publication, the parallel flat glass, which is a dust-proof glass, is made “non-perpendicular to the deflected light flux”. However, the scanning line bending correction amount by tilting the parallel flat plate glass is very small. If the parallel flat plate glass is thickened to increase the correction amount, other optical characteristics such as astigmatism are deteriorated.
[0003]
[Problems to be solved by the invention]
The present invention relates to an optical scanning device that simultaneously writes a plurality of images with a plurality of deflected light beams, to reduce the cost of the optical scanning device by sharing an optical deflector with respect to the plurality of light beams, and to the optical scanning device. It is an object to construct a compact.
[0004]
Another object of the present invention is to effectively reduce the influence of the bending of the scanning line in addition to the above problem.
[0005]
[Means for Solving the Problems]
The optical scanning device according to the present invention is formed as “a light source, a coupling lens for coupling a light beam from the light source to a subsequent optical system, and a light beam coupled by the coupling lens as a line image that is long in the main scanning direction. A first image forming system, an optical deflector having a deflecting reflecting surface in the vicinity of the image forming position of the line image, and deflecting a reflected light beam by the deflecting reflecting surface at an equiangular velocity, and a light beam deflected by the optical deflector And a second imaging system that makes the optical scanning by the light spot constant, and is characterized by the following points (Claim 1). ).
[0006]
That is, there are a plurality of “light source side optical systems” including a light source, a coupling lens, and a first imaging system, and two sets of light source side optical systems for guiding a light beam to the same deflection reflection surface of the optical deflector are “deflection”. It is arranged on the opposite side of the plane perpendicular to the rotation axis of the reflection surface, and after being guided to the common deflection reflection surface from the two sets of light source side optical systems, it is further reflected by the deflection reflection surface. Each light source side optical system is arranged so that the two guided light beams intersect within a plane including two light beams, and each light beam deflected by these common deflecting and reflecting surfaces is subjected to the second image formation. Optical scanning is performed on different parts to be scanned depending on the system.
The “main scanning corresponding direction” is a direction corresponding to the main scanning direction on the optical path from the light source to the scanned portion with respect to each light beam, and the direction corresponding to the sub scanning direction on the optical path is defined as the sub scanning corresponding direction. Called.
As the “optical deflector”, a rotating polygon mirror, a rotating single mirror or a rotating dihedral mirror can be used.
The optical scanning device of the present invention can be applied to a color image forming apparatus described later, and can be applied to a two-color image forming apparatus and a multicolor image forming apparatus.
[0007]
The “position where the light beams guided to the common deflecting / reflecting surface by the two sets of light source side optical systems intersect” may be between the deflecting / reflecting surface and the second imaging system. It may be the position of the second imaging system.
4. The optical scanning device according to claim 1, 2 or 3, wherein the light source side optical system has four sets, and the light source side optical systems are "two sets in pairs" to form each pair of light source side optical systems. Yellow, magenta, cyan, black or red, green for “image formation that generates a full-color image by multiple transfer” for guiding the light flux from each to a common deflecting reflection surface, and the light flux from each light source side optical system, It can be configured to be used as a luminous flux for writing four images of blue and black.
In this case, each pair of the light source side optical systems forming two pairs can be “disposed on the opposite sides with respect to the rotation axis of the rotary polygon mirror as the optical deflector”.
[0008]
  In the optical scanning device according to claim 1, the second imaging system that guides and images the light beams deflected by the common deflecting and reflecting surface on different scanned parts is “guides the deflected light flux to the scanned part”. On the optical path from the common deflecting reflection surface to each scanned part so that “the bending of the scanning line is in the same direction” on each scanned part, with one or more mirrors for bending the optical path on the “optical path” The number of mirrors for bending the optical path arranged in the optical path can be made different for each optical path.
  The second optical system also has a main lens for equalizing the optical scanning speed common to the two light beams deflected by the same deflecting reflection surface, and a main scanning corresponding direction and a sub-scan corresponding direction which are individually provided for each light beam. It is an anamorphic long lens having a “toroidal surface with different curvature radii”, and has an auxiliary lens that is combined with the main lens and has a conjugate relationship between the vicinity of the position of the deflecting reflecting surface and the scanned portion in the sub-scanning corresponding direction. Each of the above auxiliary lensesThe intersection of the optical axis and the lens surface is connected in the longitudinal direction and is convex with respect to the central plane.It has a bend in the bus, and the direction of the bend in the busFor each light path to reduceHas been placed.
  The second imaging system may include a pressing unit that bends the long lens so as to correct the bending of the bus bar with respect to the long lens included in each scanned portion. In this case, the long lens is bent so that its focal line is on the attachment reference side at both ends of the optical scanning, and away from the attachment reference side at the center of the optical scanning, with respect to the attachment reference side along the longitudinal direction. It can be the shape which is (claim 7).
  An image forming apparatus can be configured using the optical scanning device according to any one of the first to seventh aspects.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
In FIG. 1, the direction orthogonal to the drawing is the “direction parallel to the rotation axis” of the rotary polygon mirror 4 as the “optical deflector”. Reference numeral 1a in FIG. 1 represents two light sources. The two light sources overlap each other when viewed from the direction of the rotation axis. Similarly, reference numeral 2a represents "two coupling lenses overlapping each other when viewed from the direction of the rotation axis", and reference numeral 3a represents "two cylindrical lenses overlapping each other when viewed from the direction of the rotation axis". Yes. That is, the two light sources 1a, the two coupling lenses 2a, and the two cylindrical lenses 3a form “two sets of light source side optical systems”. Exactly the same, the two light sources 1b, the two coupling lenses 2b, and the two cylindrical lenses 3b form two sets of light source side optical systems that overlap each other when viewed from the rotational axis direction of the rotary polygon mirror 4.
[0010]
The “two sets of light source side optical systems” by the two light sources 1a, the two coupling lenses 2a, and the two cylindrical lenses 3a share the deflecting / reflecting surface 41 of the rotary polygon mirror 4 with two light sources 1b, two cups. The “two sets of light source side optical systems” using the ring lens 2 b and the two cylindrical lenses 3 b share the deflection reflection surface 42 of the rotary polygon mirror 4. Each of the cylindrical lenses is a “first imaging system”, but it can be replaced with a reflecting mirror having a concave cylinder surface as a mirror surface.
[0011]
FIG. 3 shows an arrangement state of two sets of light source side optical systems for guiding a light beam to the deflecting / reflecting surface 41 of the rotary polygon mirror 4. The vertical direction in the figure is the direction of “the rotational axis of the rotating polygon mirror 4”, and the two light source side optical systems overlap each other in this direction. Reference numerals 105 and 115 denote two light source unit units. The light source unit 105 includes a semiconductor laser 101 as a light source and a coupling lens 102 that couples a light beam from the semiconductor laser 101. The light source unit 115 includes a semiconductor laser 111 as a light source and a coupling lens 112 that couples a light beam from the semiconductor laser 111. The light flux from each semiconductor laser is coupled by a corresponding coupling lens, and in this embodiment, it becomes a substantially “parallel light flux”, but depending on the optical design of the first imaging system and the second imaging system. The coupled light beam may be a divergent light beam or a convergent light beam. The substantially parallel light beam emitted from the light source unit 105 is converged in the sub-scanning corresponding direction by the cylindrical lens 103 which is the first imaging system, and in the vicinity of the deflection reflection surface 41, in the main scanning-corresponding direction (in FIG. The image is formed as a long line image in the direction orthogonal to the above. Similarly, a substantially parallel light beam emitted from the light source unit 115 is converged in the sub-scanning corresponding direction by the cylindrical lens 113 and formed as a long line image in the vicinity of the deflection reflecting surface 41 in the main scanning corresponding direction.
As shown in FIG. 3, a light source side optical system including a light source 101, a coupling lens 102, and a cylindrical lens 103, and a light source side optical system including a light source 111, a coupling lens 112, and a cylindrical lens 113 are optical deflectors. It exists on both sides of the plane 4A orthogonal to the rotation axis of a certain rotating polygon mirror 4. In particular, in this embodiment, the two sets of light source side optical systems that guide the light beam to the same deflecting / reflecting surface are symmetrically arranged with the plane 4A as a symmetry plane.
[0012]
1 and FIG. 3, the two light sources 1a in FIG. 1 represent the semiconductor lasers 101 and 111, the two coupling lenses 2a represent the coupling lenses 102 and 112, and the two cylindrical lenses 3a represent The cylindrical lenses 103 and 113 are shown. The two light source side optical systems (which share the deflecting reflection surface 42) by the two light sources 1b, the two coupling lenses 2b, and the two cylindrical lenses 3b in FIG. This is the same as the two sets of light source side optical systems.
[0013]
In FIG. 1, the two light beams reflected by the deflecting reflecting surface 41 are deflected at a constant angular velocity by the constant speed rotation of the rotary polygon mirror 4, and are passed through the two lenses 5a and 6a constituting the second imaging system. The light is condensed as a light spot on the scanned portion 7a, and the scanned portion 7a is optically scanned at a constant speed. The to-be-scanned portion 7a is “in fact, two scanned portions in which the two light beams deflected by the deflecting reflecting surface 41 are separately optically scanned are collectively shown”.
Similarly, the two light beams reflected by the deflecting reflecting surface 42 are scanned through the two lenses 5b and 6b constituting the second image forming system 7b (two scanned objects in which each light beam is individually scanned. The light is condensed as a light spot on the upper portion of the portion 7b and the scanned portion 7b is optically scanned at a constant speed.
[0014]
FIG. 2 shows a state where a “color image forming apparatus” to which the optical scanning apparatus shown in FIG. 1 is applied is viewed from the main scanning corresponding direction. In order to avoid the complexity of the drawing, the illustration of the light source side optical system is omitted.
In FIG. 2, the rotating polygon mirror 4 simultaneously deflects four light beams L1, L2, L3, and L4 from four independent light sources. The light beams L1 and L2 are deflected by the same deflecting / reflecting surface (deflecting / reflecting surface 41 in FIG. 1) of the rotating polygon mirror 4, and the light beams L3 and L4 are deflected by the same deflecting / reflecting surface (deflecting / reflecting surface 42 in FIG. 1) of the rotating polygon mirror 4. Is done.
The deflected light beam L1 is transmitted through the main lens 5a, the optical path is bent by the mirror 91a, is transmitted through the auxiliary lens 6K, and enters the image forming unit 10K. When the light beam L2 is deflected by the rotary polygon mirror 4, it passes through the main lens 5a, the optical path is bent by the mirror 81a, passes through the auxiliary lens 6C, the optical path is bent again by the mirror 82a, and enters the image forming unit 10C. . When the light beam L3 is deflected by the rotary polygon mirror 4, it passes through the main lens 5b, the optical path is bent by the mirror 91b, passes through the auxiliary lens 6Y, and enters the image forming unit 10Y. When deflected, the light beam L4 passes through the main lens 5b, bends the optical path by the mirror 81b, passes through the auxiliary lens 6M, is bent again by the mirror 82b, and enters the image forming unit 10M.
[0015]
The image forming units 10K, 10C, 10M, and 10Y are “same structurally”, and toner colors used for development are different. Black toner is used in the image forming unit 10K, and cyan toner, magenta toner, and yellow toner are used in the image forming units 10C, 10M, and 10Y, respectively.
Since each image forming unit also operates in common, the “image forming process in the image forming unit 10Y” will be described as an example. The photoconductive photosensitive member 100Y provided in the image forming unit 10Y is drum-shaped, is rotated counterclockwise, is uniformly charged by the charging roller 103 as charging means, and a yellow latent image is written by the light beam L3. . The written yellow latent image is developed with yellow toner by the developing device 105 to become a yellow toner image. That is, the photosensitive surface of the photoreceptor 100Y is a “scanned portion” for the light beam L3. Similarly, in the image forming unit 10K, a black latent image is written and developed with black toner to form a black toner image, and a cyan toner image and a magenta toner image are formed in the image forming units 10C and 10M, respectively. Is done. The optically scanned portions of the photoconductors of the image forming units 10K and 10C are the scanned portions indicated by reference numeral 7a in FIG. 1, and the optically scanned portions of the photoconductors of the image forming units 10M and 10Y are illustrated in FIG. 1 is a scanned portion denoted by reference numeral 7b.
A sheet-like recording medium (recording paper, an overhead projector sheet or the like) S carrying the toner images of these colors is transferred to transfer / conveying means (not shown) of the conveying means and a transfer means for applying a transfer electric field from the back side thereof. In combination, the toner images are conveyed in the direction of the arrow, and black, cyan, magenta, and yellow toner images are sequentially superimposed and transferred. On the recording medium S, the color image formed as described above is fixed by fixing means (not shown) and discharged outside the apparatus.
[0016]
The embodiment described with reference to FIGS. 1, 2 and 3 is coupled by a light source, a coupling lens for coupling a light beam from the light source to a subsequent optical system, and the coupling lens. A first imaging system that forms a light beam as a long line image in the direction corresponding to the main scanning, and a light that has a deflecting reflection surface in the vicinity of the imaging position of the line image and deflects the reflected light beam by the deflecting reflection surface at a constant angular velocity. An optical scanning device having a deflector and a second imaging system for condensing a light beam deflected by the optical deflector as a light spot on a scanned portion and making the optical scanning by the light spot constant. .
[0017]
  This optical scanning device includes a plurality of sets of light source side optical systems including a light source, a coupling lens, and a first imaging system, and two sets of light source side optical systems that guide a light beam to the same deflection reflection surface of the optical deflector 4. Are arranged on opposite sides to the plane 4A (FIG. 3) orthogonal to the rotation axis of the deflecting / reflecting surface, guided to the common deflecting / reflecting surface from the two sets of light source side optical systems, and then Each light source side optical system is arranged so that the two guided light beams intersect each other in a plane including the two light beams reflected by the deflecting reflecting surface (see FIG. 2), and deflected by the common deflecting reflecting surface. Each of the luminous fluxes optically scans different scanned parts by the second imaging system.
  As described above, the “second imaging system” has a two-lens configuration including a main lens and an auxiliary lens.Further, the light flux from each light source is formed as a long line image in the main scanning corresponding direction at the position of the deflecting reflection surface of the rotary polygon mirror 4, and the second image forming system uses this line image as an object point in the sub scanning corresponding direction. Since the light spot is imaged on the scanned portion, the above-described embodiment has a function of correcting the “surface collapse” of the rotary polygon mirror 4.
[0018]
As described above, the two light source side optical systems having a common deflecting / reflecting surface are arranged on the opposite sides of the plane perpendicular to the rotation axis of the deflecting / reflecting surface (plane 4A in FIG. 3). After the light is guided from the light source side optical system to the common deflecting / reflecting surface, the two guided light beams intersect within the plane including the two light beams reflected by the deflecting / reflecting surface (see FIG. 2). Therefore, “layout interference” between the two light source unit units 105 and 115 can be prevented.
If the layout of the light source side optical system is as described in JP-A-3-53213, the surface accuracy of the mirror disposed between the light source and the rotary polygon mirror needs to be extremely high. In order to prevent interference, it is necessary to set the distance between the light source unit units to 15 mm or more. In this case, it is necessary to increase the width of the deflecting reflecting surface of the rotary polygon mirror in the sub-scanning corresponding direction. If the width is increased, the mass of the rotary polygon mirror increases, and the rotational efficiency increases as the mass increases. The load on the rotary drive motor increases, and a large torque motor is required, resulting in high costs.
[0019]
In order to avoid the layout interference between the two light source unit units that make the light beams incident on the common deflecting / reflecting surface, a layout as shown in FIG. 4 is conceivable. Since the relationship between the image system and the light source unit is different for each light source unit (α, β in the figure), if the arrangement of the second imaging system 5a is optimized for one light source unit, the other light source The image plane is tilted with respect to the light beam from the unit, and the image formation performance is deteriorated and the light spot diameter is increased.
[0020]
In the present invention, the two light beams guided and reflected by the common deflecting / reflecting surface are “crossed in a plane including these two reflected light beams”. As shown in FIG. 6, when the crossing portion is positioned between the deflecting / reflecting surface 41 and the second imaging system (the main lens 5a thereof), the rotating polygon mirror 4 and the second connecting mirror are arranged. It is not necessary to make the “width in the sub-scanning corresponding direction (vertical direction in FIG. 6)” of the image system too thick.
[0021]
As shown in FIG. 5, when the crossing position of the light beams L1 and L2 is in the vicinity of the deflecting / reflecting surface 41, the axial size of the rotary polygon mirror 4 may be the same as that of the single beam. The same as in the case of the conventional single beam method can be used, but on the other hand, it is necessary to increase the “effective diameter in the sub-scanning direction” of the second imaging system 5a, and the cost is reduced by the rotary polygon mirror. The cost of the second imaging system becomes higher.
[0022]
As shown in FIG. 7, when the crossing positions of the light beams L1 and L2 guided to the common deflecting / reflecting surface 41 by the two sets of light source side optical systems are substantially the positions of the second imaging system 5a. (Claim 3) Since it is not necessary to increase the width of the second imaging system 5a in the sub-scanning corresponding direction, an increase in cost of the second imaging system can be suppressed, and both the light beams L1 and L2 are in the second imaging system. Therefore, the optical performance of the second imaging system can be effectively utilized.
[0023]
In the embodiment described with reference to FIGS. 1 to 3, there are four sets of light source side optical systems, two sets of these light source side optical systems are paired, and the light source side optical systems forming each pair are respectively Are guided to the common deflecting / reflecting surface 41 or the deflecting / reflecting surface 42, and the light beams from the respective light source side optical systems are yellow, magenta, cyan, black for image formation for generating a full color image by multiple transfer. Are used as light beams for writing four images (claim 4), and each pair of two pairs of light source side optical systems is "opposite to each other" with respect to the rotation axis of the rotary polygon mirror 4 as an optical deflector. (Claim 5).
[0024]
By the way, when the two light beams deflected by the same deflecting and reflecting surface intersect each other as in the optical scanning device of the present invention, the incident direction of each deflected light beam is relative to the optical axis of the second imaging system. Since it inclines in the sub-scanning corresponding direction, the scanning line that is the movement locus of the light spot in the scanned portion inevitably bends. This “bending of the scanning line” causes distortion in the image to be written, so it is necessary to suppress the bending as small as possible. In the case of the embodiment as shown in FIG. 2, the second imaging system has a common main body for the two light beams L1 and L2 (or the light beams L3 and L4) deflected by the same deflection reflecting surface. The lens 5a (or the main lens 5b) and auxiliary lenses 6K and 6C (or auxiliary lenses 6Y and 6M) provided individually for the light beams L1 and L2 (or the light beams L3 and L4) are configured. In such a case, the scanning lenses can be effectively reduced by shifting the auxiliary lenses 6K to 6Y in the sub-scanning corresponding direction and adjusting the shift amount. However, even if the scanning line bending is effectively reduced in this way, the scanning line bending is not completely zero.
In the color image forming apparatus shown in FIG. 2, a line image written with each deflected light beam is visualized with toners of black, cyan, magenta, and yellow, and a color image is formed by superimposing the toner images of each color. At this time, in the respective color toner images to be superimposed on each other, if the scanning line bending directions when forming the toner images are, for example, the light beams L1 and L2 and the light beams L3 and L4 are opposite to each other, they should overlap each other. A pixel, for example, a pixel of a black toner image and a pixel of a cyan toner image are spatially separated by “bending of scanning lines bent in opposite directions” to cause a phenomenon of “color shift”. In order to avoid this, it is only necessary that “the scanning line bends in the same direction” in the scanned portion by each light beam.
[0025]
In the case of FIG. 2, the scanning line bending in each scanned portion is in the same direction for the light beams L1 and L2, and in the same direction for the light beams L3 and L4, but the light beams L1 and L2 and the light beams L3 and L4 Vice versa. This is because the set of the light beams L1 and L2 and the set of the light beams L3 and L4 are “specularly symmetrical to each other”.
In order to avoid such a problem, the layout of the optical path for the light beams L3 and L4 may be changed as shown in FIG. That is, the light beam L3 is incident on the photoconductor 100M through the mirrors 81b and 82b, and the light beam L4 is incident on the photoconductor 100Y through the mirror 91b.
[0026]
The two light beams L1 and L2 deflected by the same deflecting and reflecting surface will be described as an example. Among these light beams L1 and L2, a light beam reflected obliquely upward by the deflecting reflecting surface like the light beam L2 is “kicked”. A light beam that is reflected obliquely downward by the deflecting and reflecting surface as in the case of the light beam L1 is called a “kicking light beam”. According to this example, the light beam L3 in FIG. 8 is a kicking light beam, and the light beam L4 is a kicking light beam.
[0027]
In the kicking luminous flux and the kicking luminous flux, the incident direction with respect to the main lens of the second imaging system is reversed with respect to the optical axis of the main lens in the sub-scanning corresponding direction. Therefore, the original scanning line bend (if these light beams are imaged on a common scanned portion), the light beams L1 and L2 have opposite directions, and the light beams L3 and L4 have opposite directions. It should be.
In the above embodiment, two mirrors are used for bending the optical path for the kicking light beam L2 and the kicking light beam L4, and one mirror is used for the kicking light beam L1 and the kicking light beam L3. By “changing the number of mirrors for bending the optical path”, the directions of the scanning lines by the respective light beams are aligned in the same direction.
[0028]
  That is, the “scanning line bending state” at the positions of the optical path bending mirrors 91a, 81a, 82a, 91b, 81b, and 82b and the “scanning line bending state” at each scanned portion are denoted by reference numerals 291a, 281a, and 282a. , 291b, 281b, 282b, 200K, 200C, 200M, and 200Y. As apparent from the scanning line bending situations 200K, 200C, 200M, and 200Y, the scanning line bending in each scanned portion is in the same direction.
  That is, in the above-described embodiment, the second imaging system that guides and focuses the light beams deflected by the common deflecting / reflecting surface on different scanned parts is on the optical path that guides the deflected light flux to the scanned parts. 1 or more optical path bending reflectors, and the optical path bending provided on the optical path from the common deflecting reflection surface to each scanned part so that the scanning lines bend in the same direction on each scanned part. The number of reflectors is different for each optical path (Claim 1).
[0029]
The number of mirrors for bending the optical path is not limited to the case shown in FIG. 8, and various cases are possible depending on the layout of the apparatus. In general, the number of mirrors should satisfy the following conditions. good.
A light beam deflected simultaneously by the optical deflector is an N light beam. These deflected light beams are distinguished by a suffix: i, and the “parameter” for the i-th deflected light beam is Pi. The number of mirrors for bending the optical path provided on the optical path of the i-th deflected light beam is denoted by Mi. Parameter: When the value of Pi is “+1” for the kicking luminous flux and “−1” for the kicking luminous flux, the conditional expression:
ΣPi · Mi = 0 (i = 1 to N)
If the number of mirrors Mi is set so that is satisfied, the scanning line bending direction becomes the same in each scanned portion.
[0030]
In the example of FIG. 8, P1 = -1, P2 = + 1, P3 = -1, P4 = + 1, and M1 = 1, M2 = 2, M3 = 2, and M4 = 1.
(-1) (1) + (+ 1) (2) + (-1) (2) + (+ 1) (1) = 0
Thus, the above condition is satisfied (not satisfied with the optical arrangement of FIG. 2).
Of course, the number of optical path bending mirrors provided on the optical path should be small within the range allowed by the layout, and the example of FIG. 8 is an example in which the “minimum number” is realized.
[0031]
In each of the embodiments described above, the second imaging system is constituted by “a main lens common to two light beams deflected by the same deflecting reflection surface” and “an auxiliary lens provided individually for each light beam”. Yes. The main lens is a spherical lens, and distortion is adjusted and given to make the optical scanning speed constant. On the other hand, the auxiliary lens is an anamorphic “long lens” having a “toroidal surface with different radii of curvature in the main scanning direction and the sub-scanning direction” and is provided for each scanned portion and combined with the main lens. In the sub-scanning corresponding direction, the vicinity of the deflecting reflection surface position and the scanned portion are in a conjugate relationship.
[0032]
Such a long lens is generally manufactured by plastic molding. In that case, due to the special shape of the long lens, a shape error called “bending of the busbar” occurs in the actually manufactured auxiliary lens. In FIG. 9, reference numeral 6 indicates an example of the auxiliary lens. In this figure, the “bus line” is the intersection of the actual optical axis and the lens surface in the longitudinal direction (the meaning is different from the original bus line, but there is no appropriate terminology). Therefore, in this specification, the curve defined as described above is referred to), and the curve is convex to one side with respect to the center plane.
[0033]
  When such an auxiliary lens having a “bus curve” is used, the curve of the bus line is one of the causes of the scan line curve. For this reason, conventionally, auxiliary lenses with bent busbars are discarded as “defective products”.RuIn the present invention, the bending of the bus is effectively used. In other words, the bending of the bus (bent so as to be on the attachment reference side at both ends of the optical scanning, and away from the attachment reference side at the center of the optical scanning with respect to the attachment reference side along the longitudinal direction). In general, since it has the effect of “promoting scanning line bending in the same direction as the bending of the bus line”, the bending direction of the bus line is determined by bending the scanning line.For each light path to reduceIf the auxiliary lens is provided, the scanning line bending is corrected by the bus line bending, and the scanning line bending in each scanned portion can be further reduced.
[0034]
  10 shows the reference planes of the auxiliary lenses 6K to 6Y having the bus-line bends as shown in FIG. 9 (surfaces on the “attachment reference side along the longitudinal direction”), and the scan lines are bent in the same direction in each scanned portion. To beDetermine for each optical pathThis is an example of setting.
[0035]
Further, as shown in FIG. 11, the auxiliary lens 6 that is a long lens is intentionally formed to bend the bus and adjust the direction of the scan line as described above. By supporting both ends in the longitudinal direction and applying pressure by an appropriate “pressing means” to “flexure” the auxiliary lens 6, the bending of the bus line is reduced or emphasized, and the bending of the scanning line is corrected. be able to.
[0036]
In one example, the scan line is corrected almost completely by bending the scan line curve of 0.16 mm by 0.1 mm in the direction orthogonal to the longitudinal direction (direction corresponding to the sub scan). It was possible to straighten.
[0037]
In the above embodiment, a case where one light beam is emitted from one light source has been described. However, a plurality of light beams are emitted from one light source so that a plurality of lines are simultaneously scanned in each scanned portion. It may be.
[0038]
【The invention's effect】
As described above, according to the present invention, a novel optical scanning device can be provided.
In the optical scanning device of the present invention, there are a plurality of sets of light source side optical systems including a light source, a coupling lens, and a first imaging system, and two sets of light source side optics for guiding a light beam to the same deflection reflection surface of the optical deflector. The system is arranged on opposite sides with respect to the plane orthogonal to the rotation axis of the deflecting reflecting surface, guided from the two sets of light source side optical systems to the common deflecting reflecting surface, and then reflected by the deflecting reflecting surface. Since each light source side optical system is arranged so that the two guided light beams intersect in the plane including the two light beams, the optical scanning is performed by using a common optical deflector for the plurality of light beams. The cost of the apparatus can be reduced, and the optical scanning apparatus can be made compact by preventing layout interference between the light source units of each light source side optical system.
[0039]
In the invention according to claim 2, since the crossing position of the light beams guided to the common deflecting / reflecting surface by the two sets of light source side optical systems is between the deflecting / reflecting surface and the second imaging system, the rotation is performed. It is not necessary to make the “width in the sub-scanning direction” of the polygon mirror and the second imaging system too thick, and the rotary polygon mirror, which is an optical deflector, does not require a large torque motor, thus reducing the cost of the optical scanning device. Is done.
[0040]
In the invention according to claim 3, since the crossing position of the light beams guided to the common deflecting / reflecting surface by the two sets of light source side optical systems is substantially the position of the second imaging system, It is not necessary to increase the width in the sub-scanning corresponding direction, the cost increase of the second imaging system can be suppressed, and each deflected light beam passes through the vicinity of the optical axis of the second imaging system. Optical performance can be utilized effectively.
[0041]
According to the fourth and fifth aspects of the invention, “image formation in which a full-color image is generated by multiple transfer” can be realized easily and inexpensively.
[0042]
  In addition, according to the first to seventh aspects of the invention, the influence of the bending of the scanning line can be effectively reduced, and image formation with good performance can be realized by using the optical scanning device according to these inventions.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining one embodiment of the present invention.
FIG. 2 is a diagram for explaining a case where the embodiment of FIG. 1 is applied to a color image forming apparatus.
FIG. 3 is a diagram for explaining a deployed state of a set of light source side optical systems in the embodiment of FIG. 1;
FIG. 4 is a diagram for explaining the proportionality of the effect of the first aspect of the present invention;
FIG. 5 is a diagram for explaining the proportionality of the effect of the invention according to claim 2;
FIG. 6 is a diagram for explaining one embodiment of the invention as set forth in claim 2;
FIG. 7 is a view for explaining one embodiment of the invention as set forth in claim 3;
FIG. 8 is a view for explaining one embodiment of the first aspect of the present invention;
FIG. 9 is a view for explaining bending of a bus of a long lens as an auxiliary lens.
FIG. 10It is a figure for demonstrating correction | amendment of the curve of the scanning line by the elongate lens which has the curve of a bus line.
FIG. 11Claim 6It is a figure for demonstrating description invention.
[Explanation of symbols]
  101, 111 semiconductor laser
  102,112 coupling lens
  103,113 Cylindrical lens
  4 rotating polygon mirrors
  41 deflection reflective surface

Claims (8)

A light source, a coupling lens that couples a light beam from the light source to a subsequent optical system, and a first imaging system that forms the light beam coupled by the coupling lens as a long line image in a main scanning correspondence direction An optical deflector having a deflecting reflection surface in the vicinity of the image formation position of the line image and deflecting a reflected light beam from the deflecting reflection surface at an equiangular velocity, and a light beam deflected by the optical deflector to be scanned And a second imaging system for condensing the light spot with the light spot and making the light scanning with the light spot at a constant speed,
There are a plurality of light source side optical systems including a light source, a coupling lens, and a first imaging system,
The two sets of light source side optical systems for guiding the light beam to the same deflecting / reflecting surface of the optical deflector are arranged on opposite sides with respect to a plane perpendicular to the rotation axis of the deflecting / reflecting surface,
After the light is guided from the two sets of light source side optical systems to the common deflecting / reflecting surface, the two guided light beams intersect within the plane including the two light beams reflected by the deflecting / reflecting surface. Each light source side optical system is deployed,
Each light beam deflected by these common deflecting and reflecting surfaces optically scans different scanned parts by the second imaging system,
The second imaging system that guides and images the light beams deflected by the common deflecting / reflecting surface on different scanning parts is common to the two light beams deflected by the same deflecting / reflecting surface and performs optical scanning at a constant speed. Anamorphic long lens that has a toroidal surface with different curvature radii in the main scanning corresponding direction and the sub-scanning corresponding direction provided separately for each light beam, and combined with the main lens in the sub-scanning corresponding direction. And an auxiliary lens having a conjugate relation between the vicinity of the position of the deflecting reflection surface and the scanned portion, and one or more optical path bending mirrors on the optical path for guiding the deflected light beam to the scanned portion,
The number of optical path bending mirrors provided on the optical path from the common deflecting / reflecting surface to each scanned part is made different in each optical path so that the scanning line bends in each scanned part have the same direction. And each of the auxiliary lenses has a curve of the generating line that is convex with respect to the central plane in the intersection of the optical axis and the lens surface in the longitudinal direction ,
An optical scanning device characterized in that the direction of bending of the bus bar is determined for each optical path so as to reduce the scanning line bending. The optical scanning device according to claim 1,
An optical scanning device characterized in that a crossing position of light beams guided to a common deflecting / reflecting surface by two sets of light source side optical systems is between the deflecting / reflecting surface and the second imaging system. The optical scanning device according to claim 1,
An optical scanning device characterized in that a position where light beams guided to a common deflecting / reflecting surface by two sets of light source side optical systems intersect is substantially a position of a second imaging system. The optical scanning device according to claim 1, 2 or 3.
There are four sets of light source side optical systems, two pairs of these light source side optical systems are paired, and each pair of light source side optical systems is guided to a common deflecting and reflecting surface,
The luminous flux from each light source side optical system is used as a luminous flux for writing four images of yellow, magenta, cyan, black or red, green, blue, and black for image formation that generates a full color image by multiple transfer. An optical scanning device. The optical scanning device according to claim 4.
An optical scanning device characterized in that each pair of two pairs of light source side optical systems is arranged on the opposite side to the rotation axis of a rotary polygon mirror as an optical deflector. The optical scanning device according to any one of claims 1 to 6,
An optical scanning device comprising: a pressing unit that bends the long lens so as to correct the bending of the bus for each long lens of the second imaging system. The optical scanning device according to claim 6.
The long lens has its focal line bent at the attachment reference side at both ends of the optical scan and at the center of the optical scan away from the attachment reference side with respect to the attachment reference side along the longitudinal direction. An optical scanning device.   An image forming apparatus comprising the optical scanning device according to claim 1.

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