JP5093075B2 - Optical scanning apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to an optical scanning device and an image forming apparatus including the same.

  Patent Document 1 describes an optical scanning device that irradiates four photoconductors with light beams to form an electrostatic latent image on each photoconductor.

More specifically, this light scanning device is provided with four light sources. The light beams emitted from the four light sources are deflected and scanned by a rotary polygon mirror, and are folded by eight plane mirrors to be reflected on the photosensitive member. Is irradiated with a light beam.
JP 2003-149573 A

  An object of the present invention is to reduce the weight of an optical scanning device.

An optical scanning device according to a first aspect of the present invention includes a plurality of light sources that emit a light beam and a plurality of reflection surfaces, and reflects the light beam emitted from the light source by rotating to reflect the main surface of the surface to be scanned. A rotating polygon mirror that scans in the scanning direction and a plurality of light beams reflected by the reflecting surface of the rotating polygon mirror are transmitted in common, and a light beam that is reflected by the reflecting surface and scanned at an equal angle is provided for each light beam. A resinous optical means for scanning at a constant speed on the surface to be scanned, a separating means for separating the optical paths of a plurality of light beams transmitted through the optical means, and a light beam separated by the separating means, respectively. A plurality of curved reflecting elements that form a light beam on each scanned surface, and the optical means includes a first lens member on which the light beam reflected by the reflecting surface of the rotary polygon mirror is incident; The first lens member The first lens member is composed of a second lens member on which the transmitted light beam is incident, and the first lens member on which the light beam is incident and the first lens member on which the light beam incident from the first incident surface is emitted. The first exit surface is formed of an anamorphic aspheric surface, and the light beam incident on the second entrance surface and the second entrance surface of the second lens member on which the light beam transmitted through the first lens member enters is emitted. The second exit surface of the second lens member is formed of an anamorphic aspheric surface, and the first entrance surface, the first exit surface of the first lens member, the second entrance surface of the second lens member, and the second. The paraxial curvature of the first lens member and the second lens member in the sub-scanning direction of the scanned surface of the exit surface is a negative curvature,
Radius of curvature of the first entrance surface <curvature radius of the first exit surface,
The relationship of the radius of curvature of the second entrance surface <the radius of curvature of the second exit surface is satisfied,
The first lens member and the second lens member are configured to reduce a relative angle between light beams in the sub-scanning direction, and to separate a plurality of light beams emitted and transmitted from the light source after being transmitted. It is characterized by going to.
According to a second aspect of the present invention, there is provided the optical scanning device according to the first aspect, wherein a plurality of light beams are folded back in substantially the same direction between the optical means and the separating means on the optical path of the light beam. A folding member is provided.
According to a third aspect of the present invention, there is provided an image forming apparatus comprising: the optical scanning device according to the first or second aspect; and an image holding body including a scanned surface on which an optical beam emitted from the optical scanning device performs image scanning. , Provided.

  An image forming apparatus employing an example of an optical scanning device according to a first embodiment of the present invention will be described with reference to FIGS.

(overall structure)
As shown in FIG. 9, the image forming apparatus 10 includes four process cartridges 13Y, 13M, 13C, and 13K of yellow (Y), magenta (M), cyan (C), and black (K) in the horizontal direction. Are arranged in parallel at regular intervals. In addition, when it is necessary to distinguish YMCK, it demonstrates by attaching | subjecting any one of Y, M, C, and K after a code | symbol, and when it is not necessary to distinguish YMCK, YMCK is abbreviate | omitted.

  These four process cartridges 13Y, 13M, 13C, and 13K are all configured in the same manner, and a photoreceptor 16 that is rotationally driven at a predetermined speed, and a charging roll that uniformly charges the surface of the photoreceptor 16 44 (see FIG. 8) and a cleaning device 18 for cleaning the surface of the photosensitive member 16. The process cartridge 13 is integrally formed as a unit, and is configured to be individually replaceable from the main body 10 </ b> A of the image forming apparatus 10.

  Further, the optical scanning device 36 disposed below the process cartridge 13 exposes an image corresponding to a predetermined color on the surface of the photoconductor 16 to form an electrostatic latent image. Details of the optical scanning device 36 will be described later.

  As shown in FIG. 8, the electrostatic latent image formed on the surface of the photosensitive member 16 is yellow (Y), magenta (M), cyan (C), black by the developing roll 17A provided in the developing unit 17, respectively. It is developed as a toner image of each color of (K).

  Further, as shown in FIG. 9, the toner images of the respective colors formed on the surface of the photoconductor 16 are transferred to four primary images on the surface of the intermediate transfer belt 25 of the transfer unit 22 arranged above each process cartridge 13. The images are sequentially transferred by the transfer rolls 26Y, 26M, 26C, and 26K. These primary transfer rolls 26Y, 26M, 26C, and 26K are disposed on the back side of the intermediate transfer belt 25 corresponding to the photosensitive member 16 of each process cartridge 13Y, 13M, 13C, and 13K.

  Further, the intermediate transfer belt 25 is wound around the drive roll 27, the tension roll 24, and the backup roll 28 with a constant tension, and is predetermined in the direction of the arrow by the drive roll 27 that is rotated by a motor (not shown). It is designed to circulate at a speed of.

  Further, the yellow (Y), magenta (M), cyan (C), and black (K) toner images transferred to the surface of the intermediate transfer belt 25 are full-color, and a secondary transfer roll 29 that is in pressure contact with the backup roll 28. Thus, the sheet material P transferred to the sheet material P as a recording medium and transferred with the toner images of these colors is conveyed to the fixing device 31 disposed above. The secondary transfer roll 29 is in pressure contact with the side of the backup roll 28 and is configured to secondary-transfer toner images of each color onto the sheet material P conveyed from below to above. Thereafter, the sheet material P to which the toner image has been transferred is fixed by the fixing device 31 and then discharged by a discharge roll 32 to a discharge tray 33 provided on the upper portion of the main body 10A.

  The sheet material P is a sheet conveyance path 37 in a state in which sheets of a predetermined size are separated one by one by a nudger roll 35 and a separation conveyance feed roll 30 from a sheet feeding device 34 disposed inside the main body 10A. Then, it is conveyed to the registration roll 38 and stopped. The sheet material P fed from the paper feeding device 34 is sent to the secondary transfer position of the intermediate transfer belt 25 by a registration roll 38 that rotates at a predetermined timing.

  When images are formed on both sides of the sheet material P, the sheet material P on which the image is fixed on one side is not discharged as it is to the discharge tray 33 by the discharge roll 32, but the conveyance direction is changed by a switching gate (not shown). It is switched and conveyed to the duplex conveying unit 40 via the sheet conveying roll 39. In the double-sided conveyance unit 40, the sheet material P is conveyed again to the resist roll 38 in a state where the front and back of the sheet material P are reversed by a conveyance roll pair (not shown) provided along the conveyance path 41. After the image is transferred and fixed on the back surface of the paper, it is discharged to the discharge tray 33.

  On the other hand, residual toner, paper dust, and the like are removed from the surface of the photoconductor 16 after the toner image transfer process is completed by a cleaning device 18 shown in FIG. 8 to prepare for the next image forming process. The cleaning device 18 is provided with a cleaning blade 42, which removes residual toner, paper dust, and the like on the surface of the photoreceptor 16. Further, residual toner and the like are removed from the surface of the intermediate transfer belt 25 after the toner image transfer process is completed by the cleaning device 43 shown in FIG. The cleaning device 43 includes a cleaning brush 43A and a cleaning blade 43B that remove residual toner and the like.

(Main part)
Next, the optical scanning device 36 will be described in detail.

  As shown in FIG. 1, the optical scanning device 36 irradiates the four photoconductors 16Y, 16M, 16C, and 16K with the light beams LY, LM, LC, and LK, respectively, so that an electrostatic latent image is formed on the photoconductor 16. Form.

  As shown in FIG. 2, the optical scanning device 36 is provided with four light sources 50. The light source 50Y, the light source 50M, the light source 50C, and the light source 50K are a yellow light beam LY and magenta light. A beam LM, a cyan light beam LC, and a black light beam LK are emitted. In the following description, the members provided for each color are indicated by adding alphabets (Y / M / C / K) indicating the respective colors to the end of the reference numerals, but will be described without particularly distinguishing the colors. In this case, the explanation will be made by omitting the alphabet at the end of the code. In FIG. 2, the light beams LY, LM, LC, and LK are shown on the left and right sides of the drawing, respectively, but the light beam LY, LM when the right side is the scanning start side image end and the left side is the scanning end side image end. , LC, LK. Although it appears as three lines in the width direction, the outer line represents the light beam width, and the middle line represents the principal ray.

  Further, the optical scanning device 36 includes a plurality of (six in the present embodiment) reflecting surfaces 52A, and reflects the light beam L emitted from the light source 50 by being rotated by a drive motor, and the main surface on the photosensitive member 16 is reflected. A polygon mirror 52 is provided as a rotating polygon mirror that scans in the scanning direction.

  A collimator lens 54 is provided in the optical path from the light source 50 to the polygon mirror 52 so as to correspond to each light source 50. The collimator lens 54 converts the light beam L emitted from the light source 50 into parallel light.

  Further, on the downstream side of the optical paths of the four collimator lenses 54, first plane mirrors 56Y, 56M for reflecting parallel light transmitted through the collimator lenses 54 in directions substantially perpendicular to each other after passing through an opening (not shown), 56C and 56K are provided. Each light source 50 is provided at a distance in the sub-scanning direction (the depth direction shown in FIG. 2) so that the light beams LY, LM, LC, and LK do not interfere with each other. The opening (not shown) is beam shaping means, and its sub-scanning direction width is 1.2 mm for LY, LM, and LK, and 1.4 mm for LC.

  Further, one cylinder lens 57 that converges the light beam L in the sub-scanning direction and guides it to the reflecting surface 52A of the polygon mirror 52 is provided downstream of the first flat mirror 56 in the optical path. Further, a second flat mirror 58 that reflects the light beam L transmitted through the cylinder lens 57 toward the polygon mirror 52 is provided between the cylinder lens 57 and the polygon mirror 52. The cylinder lens 57 is an optical glass having a refractive index of 1.511080 at a wavelength of 785 nm, and has a convex R surface with a curvature radius of 76.662 mm on the incident side and a flat surface on the emission side with a thickness of 5 mm. The distance from the exit side of the cylinder lens 57 to the polygon mirror 52 is 145.4 mm.

  The light beams LY, LM, LC, and LK guided to the polygon mirror 52 by the second plane mirror 58 are incident obliquely (obliquely incident) in the sub-scanning direction on the polygon mirror 52 that is rotationally driven. Scanning is performed at a predetermined speed. The oblique incident angles are 4.558 ° for LY and LK and 1.468 ° for LM and LC, and each beam is incident on the center position of the reflecting surface 52A.

  As shown in FIG. 1, on the downstream side of the optical path of the polygon mirror 52, there is provided a transmissive member 59 made of plate glass through which the four light beams L reflected by the reflecting surface 52A are transmitted, and the polygon mirror 52 rotates. This suppresses the heat generated in the flow from the transmission member 59 to the downstream of the optical path.

  Further, a first incident surface 60A on which the four light beams L reflected by the reflecting surface 52A are incident and a first emission surface 60B on which the four light beams are emitted are provided downstream of the light path of the transmission member 59. A first fθ lens 60 is provided as a lens member.

  Further, on the downstream side of the optical path of the first fθ lens 60, a second incident surface 62A on which the four light beams L transmitted through the first fθ lens 60 are incident and a second emission surface 62B on which the four light beams are emitted are provided. A second fθ lens 62 as a second lens member is provided. Details of the surface shapes of the first entrance surface 60A, the first exit surface 60B, the second entrance surface 62A, and the second exit surface 62B will be described later.

  The third plane mirror 64 that reflects the four light beams LY, LM, LC, and LK is provided downstream of the optical path of the second fθ lens 62, and two optical paths downstream of the third plane mirror 64 are provided. A fourth plane mirror 66 that reflects the light beams LY and LM and a fifth plane mirror 68 that reflects the two light beams LC and LK are provided.

  A sixth plane mirror 70 that reflects the light beam LM is provided downstream of the optical path of the fourth plane mirror 66, and a seventh plane mirror 72 that reflects the light beam LC is disposed downstream of the optical path of the fifth plane mirror 68. Is provided.

  Further, on the downstream side of the optical path of the fourth plane mirror 66, the light beam LY reflected and folded by the fourth plane mirror 66 is reflected toward the photoconductor 16Y, and the light beam LY is imaged on the photoconductor 16Y. A glass cylindrical mirror 80Y is provided.

  Further, on the downstream side of the optical path of the sixth plane mirror 70, the light beam LM reflected and folded by the sixth plane mirror 70 is reflected toward the photoconductor 16M, and the light beam LM is imaged on the photoconductor 16M. A glass cylindrical mirror 80M is provided.

  Further, on the downstream side of the optical path of the seventh plane mirror 72, the light beam LC reflected and folded by the seventh plane mirror 72 is reflected toward the photoconductor 16C, and the light beam LC is imaged on the photoconductor 16C. A glass cylindrical mirror 80C is provided.

  Further, on the downstream side of the optical path of the fifth plane mirror 68, the light beam LK reflected and folded by the fifth plane mirror 68 is reflected toward the photoconductor 16K, and the light beam LK is imaged on the photoconductor 16K. A glass cylindrical mirror 80K is provided.

  By adopting the cylindrical mirror 80 having the curved surface R as described above, the number of plane mirrors can be reduced. Further, by making the cylindrical mirror 80 made of glass, the linear expansion coefficient is reduced, and the temperature characteristics (for example, focus depth performance) of the cylindrical mirror are improved. Details of the surface shapes of the cylindrical mirrors 80Y, 80M, 80C, and 80K will be described later.

  On the other hand, the end of the light beam LK emitted from the light source 50K is provided with a synchronizing light LS that is one beam of the light beam LK. The synchronizing light LS is reflected by the fifth plane mirror 68 and then the SOS mirror. The light is emitted toward the SOS sensor 92 arranged outside the image area by 90. An SOS lens 94 is provided between the SOS mirrors 90 of the SOS sensor 92, and the synchronization light LS is condensed on the SOS sensor 92 by the SOS lens 94. A control unit (not shown) controls the timing of image writing on the photoconductor 16 based on the detection timing of the synchronization light LS collected on the SOS sensor 92.

  Next, the first entrance surface 60A and the first exit surface 60B of the first fθ lens 60 shown in FIG. 3 and the second entrance surface 62A and the second exit surface 62B of the second fθ lens 62 will be described.

The first fθ lens 60 is molded from a polyolefin-based resin, and the refractive index of the first fθ lens 60 is 1.538232. Further, the optical surface range of the first fθ lens 60 is 11 × 72 mm, and the center thickness of the first fθ lens 60 is 7.5 mm. The first incident surface 60A of the first fθ lens 60 is an anamorphic aspheric surface, and the surface shape of the first incident surface 60A is:
CUX X curvature-3.142350E-02
X radius of curvature -3.182332E + 01
CUY Y curvature -2.316063E-02
Y curvature radius -4.331771E + 01
KY Y-conic constant -9.636016E + 00
AR 4th order coefficient of rotational symmetry 1.801438E-06
BR 6th order coefficient of rotational symmetry 7.418266E-07
CR 8th order coefficient of rotational symmetry 1.573881E-10
DR 10th order coefficient of rotational symmetry 5.387575E-15
KX X conic constant 1.747152E + 01
AP rotationally asymmetric fourth order coefficient 3.137927E-01
BP 6th order rotationally asymmetric coefficient -1.040577E + 00
CP rotationally asymmetric 8th order coefficient −1.1189176E + 00
DP 10th order coefficient of rotational asymmetric −9.308370E-01
Assuming that the sub-scanning direction coordinate is x and the main scanning direction coordinate is y,

  It is described by the following formula.

The first emission surface 60B of the first fθ lens 60 is an anamorphic aspheric surface, and the surface shape of the first emission surface 60B is:
CUX X curvature -3.571406E-02
X curvature radius -2.800018E + 01
CUY Y curvature -1.730603E-02
Y curvature radius -5.777833E + 01
KY Y-conic constant -1.626479E + 00
AR 4th order coefficient of rotational symmetry 2.515334E-05
BR 6th order coefficient of rotational symmetry 1.737267E-13
CR 8th order coefficient of rotational symmetry 5.969757E-14
DR 10th order coefficient of rotational symmetry -4.289673E-14
KX X conic constant 8.358856E + 00
AP rotationally asymmetric fourth order coefficient −6.697999E-01
BP 6th order coefficient of rotational asymmetric 1.266576E + 01
CP rotationally asymmetric 8th order coefficient -2.2222165E + 00
DP 10th order coefficient of rotational asymmetry -1.248030E + 00
Assuming that the sub-scanning direction coordinate is x and the main scanning direction coordinate is y,

  It is described by the following formula.

That is, the paraxial first entrance surface 60A and the first exit surface 60B of the first fθ lens 60 in the sub-scanning direction have a negative curvature,
The relationship of the radius of curvature of the first incident surface 60A <the radius of curvature of the first emission surface 60B is satisfied, and the light beam in the sub-scanning direction is converged while maintaining the distance from the adjacent light beam L. It is the composition which makes it.

The second fθ lens 62 is molded from a polyolefin resin, and the refractive index of the second fθ lens 63 is 1.538232. Further, the optical surface range of the second fθ lens 62 is 13 × 112 mm, and the center thickness of the second fθ lens 62 is 12 mm. The second incident surface 62A of the second fθ lens 62 is an anamorphic aspheric surface, and the surface shape of the second incident surface 62A is:
CUX X curvature -1.517917E-02
X curvature radius -6.587776E + 01
CUY Y curvature 2.76335E-02
Y curvature radius 3.617507E + 01
KY Y-conic constant -5.666780E + 00
AR 4th order coefficient of rotational symmetry -1.628579E-08
BR 6th order coefficient of rotational symmetry 1.50943E-10
CR 8th order coefficient of rotational symmetry 3.736799E-17
DR 10th order coefficient of rotational symmetry -2.327089E-17
KX X conic constant 4.152058E + 01
AP rotationally asymmetric fourth-order coefficient 7.152984E + 00
BP 6th order coefficient of rotational asymmetric -1.660209E + 00
CP rotationally asymmetric 8th order coefficient 3.99737E + 00
DP 10th order coefficient of rotational asymmetric -1.577818E + 00
Assuming that the sub-scanning direction coordinate is x and the main scanning direction coordinate is y,

  It is described by the following formula.

The second emission surface 62B of the second fθ lens 62 is an anamorphic aspheric surface, and the surface shape of the second emission surface 62B is:
CUX X curvature -2.328641E-02
X curvature radius -4.294351E + 01
CUY Y Curvature 1.777684E-02
Y curvature radius 5.618974E + 01
KY Y-conic constant -8.788611E + 00
AR 4th order coefficient of rotational symmetry -6.297002E-08
BR 6th order coefficient of rotational symmetry 1.004796E-09
CR 8th order coefficient of rotational symmetry 4.728069E-12
DR 10th order coefficient of rotational symmetry 4.094364E-12
KX X conic constant 1.057156E + 01
AP rotationally asymmetric fourth order coefficient 3.474053E + 00
BP 6th order rotationally asymmetric coefficient -7.3324482E-01
CP rotationally asymmetric 8th order coefficient -1.058170E + 00
DP 10th order coefficient of rotational asymmetric -1.006366E + 00
Assuming that the sub-scanning direction coordinate is x and the main scanning direction coordinate is y,

  It is described by the following formula.

That is, the paraxial second entrance surface 62A and the second exit surface 62B of the second fθ lens 62 in the sub-scanning direction have a negative curvature,
The relationship of the radius of curvature of the second entrance surface 62A <the radius of curvature of the second exit surface 62B is satisfied, and the light beam in the sub-scanning direction is converged while maintaining the distance from the adjacent light beam L. It is the composition which makes it.

  Next, the cylindrical mirrors 80Y, 80M, 80C, and 80K shown in FIG. 1 will be described.

  The optical surface range of each cylindrical mirror 80 is 10 mm × 297 mm, and the center thickness is 9 mm.

  For the cylindrical mirrors 80Y, 80M, and 80K, the distance from the reflecting surface to the scanned surface of each photoconductor 16 is set to 70 mm in terms of layout, and for the cylindrical mirror 80C, the photoconductor 16 from the reflecting surface is used. The distance to the surface to be scanned is 80 mm.

  Further, the curved surface R of the cylindrical mirror 80Y is R179.40 mm, the curved surface R of the cylindrical mirror 80M is R130.50 mm, the curved surface R of the cylindrical mirror 80C is R164.36 mm, and the curved surface R of the cylindrical mirror 80K is R146.24 mm.

  For the cylindrical mirror 80Y, the light beam LY is 1.2 mm with respect to the lens center line, and for the cylindrical mirror 80K, the light beam LK is incident with a shift of 0.8 mm with respect to the lens center line. The arrangement positions of 80Y and 80K are determined.

  Next, an introduction of the entire optical system according to the first embodiment will be described. The light source wavelength is 785 nm, the system focal length is 243.51 mm at a temperature of 20 ° C., and the image range exposed on the photoreceptor is 297 mm. In the scanning optical axis, the distance from the reflecting surface 52A to the first entrance surface 60A is 39 mm, the distance from the first entrance surface 60A to the first exit surface 60B is 7.5 mm, and the distance from the first exit surface 60B to the second entrance surface 62A is The distance from the second entrance surface 62A to the second exit surface 62B is 12 mm. The angle formed by the incident optical axis and the outgoing optical axis to the polygon mirror 60 is 60 degrees and is incident from the scanning start side.

(Function)
Next, since the imaging characteristics were evaluated using the optical scanning device 36 described above, this result will be described.

  FIG. 4 is a graph in which the scanning position of the scanning line in the main scanning direction on the surface to be scanned of the photosensitive member 16 (hereinafter referred to as a read register) is evaluated using the optical scanning device 36 according to the present embodiment. Have been described. The horizontal axis in FIG. 4 indicates the position in the main scanning direction on the surface to be scanned of the photoconductor 16, and the vertical axis indicates the position in the sub-scanning direction.

  As can be seen from the graph shown in FIG. 4, the amount of deviation of yellow (Y), magenta (M), cyan (C), and black (K) in the sub-scanning direction is ± 0.03 mm or less. It turns out that there is no problem. Further, the color difference (CRG: MAX-MIN) is 0.056 mm or less, and it can be understood that there is no practical problem with respect to the color difference (CRG).

  FIG. 5 shows the positions of the light beams LY, LM, LC, and LK in the main scanning direction when the magnification (linearity), that is, the case where the light beam L is in constant velocity motion is set to zero. A graph evaluating the deviation is described. The horizontal axis in FIG. 5 indicates the position in the main scanning direction on the surface to be scanned of the photoconductor 16, and the vertical axis indicates the amount of positional deviation.

  As can be seen from the graph shown in FIG. 5, there is no practical problem because the deviation amount of yellow (Y), magenta (M), cyan (C), and black (K) is ± 0.1 mm or less. I understand. The intercolor difference (CRG: MAX-MIN) is 0.014 mm or less, and it can be seen that there is no practical problem with respect to the intercolor difference (CRG).

  FIG. 6 shows a graph in which the focus depth in the main scanning direction at the position in the main scanning direction of the surface to be scanned of the photoconductor 16 is evaluated using the optical scanning device 36 according to the present embodiment. The horizontal axis of FIG. 6 indicates the position in the main scanning direction on the surface to be scanned of the photoconductor 16, and the vertical axis indicates the focus depth in the main scanning direction.

  As can be seen from the graph shown in FIG. 6, the variation in the focus depth in the main scanning direction is less than the range (MAX-MIN) of 2 mm.

  Further, FIG. 7 shows a graph in which the depth of focus in the sub-scanning direction at the position in the main scanning direction of the surface to be scanned of the photoconductor 16 is evaluated using the optical scanning device 36 according to the present embodiment. 7 indicates the position in the main scanning direction on the surface to be scanned of the photoconductor 16, and the vertical axis indicates the focus depth in the sub scanning direction.

  As can be seen from the graph shown in FIG. 7, the variation in the focus depth in the sub-scanning direction is 5 mm or less in the range (MAX-MIN).

  Next, an image forming apparatus employing an example of an optical scanning device according to a second embodiment of the present invention will be described with reference to FIG.

  As shown in FIG. 10, in this embodiment, unlike the first embodiment, the number of fθ lenses 100 is one.

The fθ lens 100 is molded from a polyolefin-based resin, and the refractive index of the fθ lens 100 is 1.538232. Further, the optical surface range of the fθ lens 100 is 20 × 150 mm, and the center thickness of the fθ lens 100 is 23.795 mm. Compared to the first embodiment, it has an uneven shape and is not excellent in moldability. The incident surface 100A of the fθ lens 100 is an anamorphic aspheric surface, and the surface shape of the incident surface 100A is
CUX X curvature 4.368185E-03
X curvature radius 2.289280E + 02
CUY Y curvature 1.543171E-03
Y curvature radius 6.480165E + 02
KY Y-conic constant -2.502277E + 02
AR 4th order coefficient of rotational symmetry -4.827751E-08
BR 6th order coefficient of rotational symmetry 1.105862E-08
CR 8th order coefficient of rotational symmetry -8.223891E-15
DR 10th order coefficient of rotational symmetry 5.538086E-16
KX X conic constant 6.623475E + 01
AP rotationally asymmetric fourth order coefficient -1.421623E + 00
BP 6th order coefficient of rotational asymmetric -1.009270E + 00
CP rotationally asymmetric 8th order coefficient -1.587923E + 00
DP 10th order coefficient of rotational asymmetric −9.192966E-01
Assuming that the sub-scanning direction coordinate is x and the main scanning direction coordinate is y,

  It is described by the following formula.

Further, the exit surface 100B of the fθ lens 100 is an anamorphic aspheric surface, and the surface shape of the exit surface 100B is:
CUX X curvature -6.852053E-03
X curvature radius -1.459417E + 02
CUY Y curvature -6.186020E-03
Y curvature radius -1.616548E + 02
KY Y-conic constant 2.305299E + 00
AR 4th order coefficient of rotational symmetry 5.90684E-09
BR 6th order coefficient of rotational symmetry -2.433329E-13
CR 8th order coefficient of rotational symmetry -2.3388767E-17
DR 10th order coefficient of rotational symmetry 9.841386E-19
KX X conic constant -1.316366E + 01
AP rotationally asymmetric fourth-order coefficient -2.406931E + 00
BP 6th order coefficient of rotational asymmetric -4.725344E + 00
CP rotationally asymmetric 8th order coefficient −3.269103E + 00
DP 10th order coefficient of rotational asymmetric -1.499500E + 00
Assuming that the sub-scanning direction coordinate is x and the main scanning direction coordinate is y,

It is described by the following formula.

1 is a side view showing an optical scanning device according to a first embodiment of the present invention. 1 is a plan view showing an optical scanning device according to a first embodiment of the present invention. It is the perspective view which showed the 1st f (theta) lens and 2nd f (theta) lens which were employ | adopted for the optical scanning device concerning 1st Embodiment of this invention. 1 is a graph showing optical characteristics of an optical scanning device according to a first embodiment of the present invention. 1 is a graph showing optical characteristics of an optical scanning device according to a first embodiment of the present invention. 1 is a graph showing optical characteristics of an optical scanning device according to a first embodiment of the present invention. 1 is a graph showing optical characteristics of an optical scanning device according to a first embodiment of the present invention. 1 is a side view showing the vicinity of a photoconductor of an image forming apparatus employing an optical scanning device according to a first embodiment of the present invention. 1 is a schematic configuration diagram illustrating an image forming apparatus employing an optical scanning device according to a first embodiment of the present invention. It is the perspective view which showed the f (theta) lens employ | adopted as the optical scanning device which concerns on 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 16 Photoconductor (Image holding body)
36 Optical scanning device 50 Light source 52 Polygon mirror (rotating polygon mirror)
52A Reflecting surface 59 Transmission member 60 First fθ lens (first lens member)
60A First entrance surface 60B First exit surface 62 Second fθ lens (second lens member)
62A Second entrance surface 62B Second exit surface 80 Cylindrical mirror (curved reflection element)
100 fθ lens (lens member)
100A entrance surface 100B exit surface

Claims (3)

A plurality of light sources that emit light beams;
A rotating polygon mirror that includes a plurality of reflecting surfaces, reflects the light beam emitted from the light source, and scans in the main scanning direction of the surface to be scanned;
A plurality of light beams reflected by the reflecting surface of the rotary polygon mirror are transmitted in common, and the light beam reflected by the reflecting surface and scanned at an equal angle is scanned at a constant speed on a scanning surface provided for each light beam. An optical means made of resin,
Separating means for separating a plurality of light paths of the plurality of light beams transmitted through the optical means;
A plurality of curved reflecting elements that respectively reflect the light beams separated by the separating means and image the light beams on each scanned surface;
The optical means includes a first lens member on which a light beam reflected by a reflecting surface of the rotary polygon mirror is incident, and a second lens member on which a light beam transmitted through the first lens member is incident,
The first entrance surface of the first lens member on which the light beam is incident and the first exit surface of the first lens member on which the light beam incident from the first entrance surface exits are configured by an anamorphic aspheric surface,
The second entrance surface of the second lens member on which the light beam transmitted through the first lens member enters and the second exit surface of the second lens member on which the light beam incident on the second entrance surface exits are anamorphic. Composed of aspheric surfaces,
The first lens member and the first lens surface in the sub-scanning direction of the scanned surface of the first incident surface and the first exit surface of the first lens member and the second entrance surface and the second exit surface of the second lens member. 2 The paraxial curvature of the lens member is a negative curvature,
Radius of curvature of the first entrance surface <curvature radius of the first exit surface,
The relationship of the radius of curvature of the second entrance surface <the radius of curvature of the second exit surface is satisfied,
The first lens member and the second lens member are configured to reduce a relative angle between light beams in the sub-scanning direction, and to separate a plurality of light beams emitted and transmitted from the light source after being transmitted. The optical scanning device to be advanced to . The optical scanning device according to claim 1, wherein a folding member that folds the plurality of light beams in substantially the same direction is provided between the optical unit and the separating unit on the optical path of the light beam. An optical scanning device according to claim 1 or 2 ,
An image carrier having a scanned surface on which an optical beam emitted from the optical scanning device is imaged and scanned;
An image forming apparatus.

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