JP4909687B2 - Scanning optical system, optical scanning device, and image forming apparatus - Google Patents

Description

  The present invention relates to a scanning optical system, an optical scanning device, and an image forming apparatus used in a laser printer, a digital copying machine, a fax machine, and the like.

  As problems of optical scanning devices used in image forming apparatuses such as laser printers and digital copying machines, “scanning line bending” and “scanning line inclination” are conventionally known. The scanning line is a trajectory along which the light spot moves along the optical scanning on the photosensitive medium forming the surface to be scanned, and is ideally a straight line with no inclination.

  However, in practice, a “scan line curve” in which a scan line to be a straight line is a curve or a “scan line tilt” in which the scan line is tilted occurs, and as a result, a color shift appears in the print result. In recent years, with the increase in image quality and density of color laser printers, digital color copying machines, etc., it has become a problem for optical scanning devices to reduce this color shift as much as possible.

  For example, Patent Document 1 discloses a technique for adjusting scanning line bending by pressing a substantially central portion in the longitudinal direction of a scanning lens, which is a long lens, in the sub-scanning direction.

For example, Patent Document 2 proposes a technique for adjusting a higher-order component of scanning line bending by providing three adjustment means (imine screws) along the main scanning direction of the long lens.
Japanese Patent No. 3343465 JP 2002-182145 A

  With the technique disclosed in Patent Document 1, it is possible to adjust the scan line curve of a quadratic curve, but it is not possible to correct the scan line curve of higher order components. In the technique proposed in Patent Document 2, the scanning line bending of the W-shaped high-order component can be adjusted, but it is difficult to adjust the scanning line bending of the M-shaped or asymmetrical N-shaped high-order component. There is a problem that.

  Therefore, the present invention has been made in view of the above problems, and it is possible to adjust not only a scanning line curve having a quadratic function curve but also a scanning line curve of a higher order component higher than a cubic function. An object of the present invention is to provide a scanning optical system, an optical scanning device, and an image forming apparatus.

In order to achieve such an object, the invention described in claim 1 includes an optical deflector for deflecting a light beam from a light source, at least one scanning lens for condensing the optical deflector in the vicinity of a scanned surface, deflector and the at least one folding mirror is provided between the surface to be scanned, a scanning optical system comprising the scanning lens is secondary to correct the quadratic function component of the bending of the scanning line It has a component correction means, the folding mirror is to have a high-order component correction means for correcting the high-order function ingredients and quartic function or higher-order functional components of the third-order function of the bending of the scanning line, The high-order component correction means fixes both ends and substantially the center of the folding mirror, and is an intermediate part located between the both ends and the substantially center, which is a movable part other than the both ends and the substantially center. A straight line intersecting the scanning plane and the folding mirror is rotated. Characterized by twisting a shaft.

  According to a second aspect of the present invention, in the scanning optical system according to the first aspect, the secondary component correction unit has a substantially central portion in the longitudinal direction of the scanning lens substantially perpendicular to the scanning plane. It is characterized by pressing in the direction.

According to a third aspect of the present invention, in the scanning optical system according to the first or second aspect , the scanning lens rotates the scanning lens about a lower surface or an upper surface of a substantially central portion in the longitudinal direction as a fulcrum. It has a scanning line inclination adjusting means for adjusting the inclination.

According to a fourth aspect of the present invention, in the optical scanning device, the scanning optical system according to any one of the first to third aspects is provided.

According to a fifth aspect of the present invention, the optical scanning device according to the fourth aspect has a plurality of scanning optical systems.

According to a sixth aspect of the present invention, in the image forming apparatus, the optical scanning device according to the fourth or fifth aspect is mounted.

  According to the present invention, a scanning optical system capable of adjusting not only a scanning line curve having a quadratic function curve but also a scanning line curve of a higher-order component higher than a cubic function, an optical scanning device, and An image forming apparatus is realized.

  The best mode for carrying out the present invention will be described with reference to the drawings. A scanning optical system will be described as the first embodiment, an optical scanning device as the second embodiment, and an image forming apparatus as the third embodiment.

[Embodiment 1]
1A and 1B are schematic configuration diagrams of a scanning optical system according to an embodiment of the present invention. FIG. 1A is a plan view and FIG. 1B is a side view.

  In the scanning optical system of the present embodiment, the light beam emitted from the light source 1 is coupled into a substantially parallel light beam by the coupling lens 2, enters the cylindrical lens 3, and is condensed into a substantially linear shape in the main scanning corresponding direction. , Enters the optical deflector 4.

  Then, the light beam deflected by the optical deflector 4 is transmitted through the scanning lens 5, bent in the optical path by the folding mirror 100, transmitted through the scanning lens 6, and further bent in the optical path by the folding mirrors 101 and 102. The image is formed on the surface 7.

  In addition, although it has described so that arrangement | positioning of each member may be reversed by the top view of Fig.1 (a), and the side view of FIG.1 (b) (the folding mirror 100, the scanning lens 6, and the scanning lens 6). In FIG. 1A, the members are arranged in the order in which the light beams are incident or transmitted, and FIG. 1B shows the actual arrangement. By being.

  Here, the conventional adjustment of the scanning line bending will be described. FIG. 2 is a diagram for explaining a conventional technique related to adjustment of scanning line bending. 3 and 4 are diagrams showing the state of the scanning line bending. FIG. 3 shows the scanning line bending of a high-order component (M-shaped or W-shaped) of the quartic function, and FIG. 4 shows the cubic function. The scanning line curve of the higher order component (S-shaped) is shown.

  For example, in the case of the scanning optical system having the configuration as shown in FIG. 1, the scanning line bending is adjusted by pressing the substantially central portion in the longitudinal direction of the scanning lens 6 which is a long lens in the sub-scanning direction.

  However, in the above method, the scanning line curve as shown in FIG. 3A can adjust the quadratic curve component, but the higher order component of the quartic function as shown in FIG. 3B remains. Resulting in. Further, in the case of a cubic function-like scanning line curve as shown in FIG.

  Therefore, in the present embodiment, higher-order components are adjusted by applying a force to the folding mirror to deform it. FIG. 5 is a diagram showing the configuration of the folding mirror in the scanning optical system of the present embodiment.

  For example, when the scanning line bend as shown in FIG. 3A occurs, as described above, with respect to the entire quadratic curve component, the approximate center of the scanning lens 6 shown in FIG. By a method of pressing and bending in the scanning direction, adjustment can be performed as shown in FIG. However, since the high-order component of a quartic function cannot be adjusted by the method of FIG. 2 alone, as shown in FIG. 5, both ends and the center part (near the optical axis) of the folding mirror are fixed to the housing. Then, by twisting the portion between the both ends and the central portion, the scanning line bending of the higher-order component is adjusted.

  That is, in the folding mirror 101, first, the three ends 110 and 120 and the central portion 130 are fixed to the housing. Next, the intermediate part 140 between the both ends 110 and the central part 130 and the intermediate part 150 between the both ends 120 and the central part 130, which are movable parts other than the fixed three points, are twisted. The twisting direction is a direction in which a straight line a-a ′ or a straight line b-b ′ that intersects perpendicularly with the rotation axis is rotated with a straight line intersecting the deflection scanning plane and the folding mirror 101 as the rotation axis 160.

  Here, the folding mirror 101 has been described as an example, but the present invention can be implemented using any folding mirror, and can be determined in consideration of the housing layout and assembly process.

  FIG. 6 is a graph showing a simulation result of adjustment of scanning line bending in the scanning optical system of the present embodiment. The graph shows the adjustment results in three stages: A before adjustment before correcting the scanning line bending, one-point adjustment B at the substantially central portion of the scanning lens 6, and kinking adjustment C performed by twisting the folding mirror. ing.

  A before adjustment is a result of deliberately generating a bending of the outer shape of the scanning lens 5. Further, the one-point adjustment B indicates a result of adjusting the quadratic curve of the scanning line by bending the substantially central portion of the scanning lens 6 in the sub-scanning direction. The kinking adjustment C is a quartic function-like scanning line curve by causing the intermediate portion 140 (straight line aa ′) and the intermediate portion 150 (straight line bb ′) of the folding mirror 101 to be twisted in the same direction. The result of adjusting is shown.

  The simulation of FIG. 6 represents a case where adjustment is performed for a high-order component that is a quartic function, but for the high-order component that is a cubic function as in FIG. And 150 can be adjusted in different directions, so that it is possible to adjust the scanning curve curve in a cubic curve as shown in FIG.

  7A and 7B are cross-sectional views showing the configuration in the vicinity of the scanning lens in the scanning optical system of the present embodiment, where FIG. 7A is a view seen from the optical axis direction, and FIG. Sectional drawing (c) represents a sectional view of one end of the scanning lens.

  The scanning lens 6 is sandwiched between a sheet metal 21 and leaf springs 22 and 23. In addition, the housing 51 has a protrusion 26 at a substantially central portion of the scanning lens 6, and the protrusion 26 is in contact with the scanning lens 6.

  The sheet metal 21 is fixed to the housing 51 via plate springs 24 and 25. Further, a stepping motor 32 is attached to one end of the sheet metal 21, and has a mechanism for adjusting the inclination of the scanning lens 6 with the projection 26 serving as a fulcrum by moving one end of the sheet metal 21 up and down in the sub-scanning direction.

  In this manner, the scanning optical system of the present embodiment has a configuration that can adjust not only the scanning line bending but also the scanning line inclination.

[Embodiment 2]
Next, an optical scanning device having the scanning optical system of the first embodiment will be described as a second embodiment. Hereinafter, a detailed description will be given with reference to FIGS. FIG. 8 shows a side view of the optical scanning device of the present embodiment, and FIG. 9 shows a top view of the optical scanning device 13 of the present embodiment.

  In the optical scanning device 200 of this embodiment, a polygon mirror 201 is arranged at the center, and component parts such as an LD unit, a reflection mirror, and a lens are arranged symmetrically with respect to the polygon mirror 201 as a center, so that 2 The optical path of the laser beam of the color is laid out, and the laser beam (writing laser beam) of four colors of yellow (Y), magenta (M), cyan (C), and black (K) is used in the main scanning direction by one polygon mirror. To deflect.

  The optical scanning device 200 includes a polygon mirror 201, scanning lenses 202a and 202b, a scanning lens 203 (YMCK), a first reflecting mirror 204 (YMCK), a second reflecting mirror 205 (YMCK), and a third reflecting mirror. 206 (YMCK), LD unit 207 (YMCK), cylindrical lenses 208a and 208b, fourth reflection mirror 209, synchronization detection reflection mirrors 210a and 210b, synchronization detection lenses 211a and 211b, synchronization detection sensors 212a and 212b.

  A polygon mirror 201 as a deflection scanning means is a regular polygon (regular hexagonal in the figure) reflecting mirror, which is driven to rotate by a driving motor and reflects the writing laser beam output from the LD unit 207 on the deflecting reflecting surface. Then, deflection scanning is performed in the main scanning direction.

  The regular polygon mirrors are stacked in two stages, and the upper mirror performs deflection scanning with the C laser and the Y laser, and the lower mirror performs deflection scanning with the K laser and the M laser.

  Further, the polygon mirror 201 of the present embodiment can change the rotation direction by control. In FIG. 9, the clockwise rotation direction is the forward rotation direction, and the counterclockwise rotation direction is the reverse rotation direction.

  The scanning lenses 202a and 202b are lenses provided on the optical path of each laser beam, and scan the laser beam scanned at the same angle by the polygon mirror 201 at a constant speed on the imaging surface.

  The scanning lens 203 is a lens provided on the optical path of each laser beam, and corrects the surface tilt characteristics of the polygon mirror 201.

  The first reflection mirror 204, the second reflection mirror 205, and the third reflection mirror 206 are reflection mirrors provided to guide each color laser beam onto the corresponding photosensitive drum 220.

  In FIG. 8, the floor with the polygon mirror 201 is hermetically sealed to prevent entry of dust or the like. A dust-proof glass that transmits laser light is provided on the floor surface of the floor, and each color laser light is transmitted to the photosensitive drum 220 through the dust-proof glass.

  The LD unit 207 is a writing laser light irradiation device provided independently for each color, and includes a laser diode or the like, and outputs laser light toward the polygon mirror 201.

  The cylindrical lenses 208 a and 208 b are lenses having a refractive index determined in the sub-scanning direction, and are provided for each color in the vicinity of the LD unit 37. The fourth reflecting mirror 209 is a reflecting mirror provided to guide the K laser and M laser to the polygon mirror 201.

  The synchronization detection reflection mirrors 210a and 210b are reflection mirrors provided to guide the laser light reflected by the first reflection mirror 204 at a specific position in the main scanning to the synchronization detection lenses 211a and 211b. The synchronization detection lenses 211a and 211b are lenses for converging the incident laser light guided by the synchronization detection reflection mirrors 210a and 210b to the synchronization detection sensors 212a and 212b.

  Synchronization detection sensors 212a and 212b serving as synchronization signal detection means detect the writing reference position in the main scanning direction based on the incident laser beam when the polygon mirror 201 rotates in the forward rotation direction. Specifically, a predetermined synchronization detection signal is output by the incidence of laser light. The synchronization detection sensors 212a and 212b are arranged one on each of the left and right sides, and the timing of the laser light for two colors is detected by one synchronization detection sensor.

  The deflection reflection surface of the polygon mirror 201 varies depending on the surface accuracy and angular accuracy of the manufacturing process. In order to eliminate this variation, the writing detection reference position in the main scanning direction corresponding to the deflection reflection surface is synchronized with the synchronization detection sensors 212a and 212b. To detect.

[Embodiment 3]
Subsequently, an image forming apparatus equipped with the optical scanning device according to the second embodiment will be described as a third embodiment. Hereinafter, this will be described in detail with reference to FIG. FIG. 10 is a schematic configuration diagram of the image forming apparatus of the present embodiment.

  The image forming apparatus 300 of this embodiment forms a toner image for each color of yellow (Y), magenta (M), cyan (C), and black (K), and superimposes them to form a full-color image. A tandem type image forming apparatus to be formed, which includes a document table 301, a reading device 302, an optical scanning device 303, a photosensitive drum 304 (YMCK), a charging roller 305 (YMCK), and a developing device 306 (YMCK). A drum cleaning device 307 (YMCK), an intermediate transfer belt 308, a transfer belt cleaning device 309, a transfer roller 310, a fixing device 311, a registration roller 312, a paper feed roller 313, and a paper feed tray 314. And a paper discharge roller 315 and a paper discharge tray 316.

  The document table 301 is a table on which a document to be printed, that is, a document to be read is placed. The lower surface of the document table 301 is formed from contact glass.

  The reading device 302 is a device that reads a document placed on a document table 301, and irradiates the document with laser light through a contact lens and receives reflected light from the document to read the document content.

  The optical scanning device 303 irradiates the photosensitive drum 304 corresponding to each color with a writing laser beam based on the content of the original read by the reading device 302. The configuration of the optical scanning device is as described above.

  The photosensitive drum 304 is a drum-shaped image carrier provided for each color of YMCK. Each photoconductor drum has the same diameter and is pressed against the intermediate transfer belt 308 at equal intervals.

  A charging device 305, a developing device 306, an intermediate transfer belt 308, a drum cleaning device 307, and a charge removal device (not shown) are disposed in the vicinity of the periphery of the photosensitive drum 304 along the drum rotation direction. Yes. Further, the laser beam for writing from the optical scanning device 303 is irradiated on the photosensitive drum 304 between the charging device 305 and the developing device 306.

  The charging device 305 is a roller-shaped device arranged in a non-contact manner for each color photosensitive drum, and uniformly charges the surface of the photosensitive drum 304. When the surface of the photosensitive drum 304 charged by the charging device 305 is irradiated with a writing laser beam from the optical scanning device 303, an electrostatic latent image corresponding to each color is formed on the photosensitive drum 304.

  The developing device 306 is a device that is disposed in contact with the developing roller on the photosensitive drum 304, and holds toner (developer) of a color corresponding to the photosensitive drum corresponding to each color. At the time of image formation, toner is supplied to the photosensitive drum 304, and the electrostatic latent image formed on the photosensitive drum is developed. The electrostatic latent image becomes a toner image by being developed with toner.

  The drum cleaning device 307 is a device disposed by bringing a blade (cleaning blade) into contact with the photosensitive drum 304, and residual toner remaining on the photosensitive drum after the transfer of the toner image to the intermediate transfer belt 308. Etc. are removed and recovered, and the surface of the photosensitive drum is cleaned.

  Further, a neutralization device (not shown) is provided between the drum cleaning device 307 and the charging device 305. The static eliminator neutralizes the surface of the photosensitive drum 304.

  The intermediate transfer belt 308 is an endless belt for sequentially superposing and transferring (primary transfer) each color toner image formed on the surface of the photosensitive drum 304. The respective color toner images are sequentially superimposed to form a composite color toner image on the intermediate transfer belt 308.

  The transfer belt cleaning device 309 is a device that is disposed by bringing a blade (cleaning blade) into contact with the intermediate transfer belt 308, and after transferring (secondary transfer) the composite color toner image to the recording paper to be fed. Residual toner and paper pieces remaining on the transfer belt 308 are removed and collected, and the surface of the intermediate transfer belt 308 is cleaned.

  The transfer roller 310 is a roller provided to face the intermediate transfer belt 308, and transfers the composite color toner image formed on the intermediate transfer belt 308 onto the recording paper conveyed from the paper feed tray 314 (secondary). Transfer).

  The fixing device 311 includes a heated roller, and heat-fixes the composite color toner image secondarily transferred onto the recording paper onto the recording paper.

  The registration roller 312 is a roller for aligning the leading end of the recording paper and the composite color toner image, and feeds the recording paper in accordance with the timing of the composite color toner image on the intermediate transfer belt 308.

  A paper feed roller 313 feeds recording paper. The paper feed tray 314 stores recording paper for each recording paper size. A paper discharge roller 315 discharges the recording sheet on which the composite color toner image is thermally fixed to a paper discharge tray outside the image forming apparatus 300. The paper discharge tray 316 is a tray on which the discharged recording paper is placed. An arrow starting from the paper feed tray 314 indicates a conveyance path of the recording paper.

  Note that all of the photosensitive drums 304 rotate in the same direction, and the intermediate transfer belt 308 moves in a direction opposite to the rotation direction of the photosensitive drums. The transfer roller 311 rotates in the direction opposite to that of the intermediate transfer belt 308 (the same rotation direction as that of the photosensitive drum). In FIG. 10, the photosensitive drum 304 and the transfer roller 311 rotate counterclockwise, and the intermediate transfer belt 308 rotates clockwise.

  The above-described embodiment is a preferred embodiment of the present invention, and the scope of the present invention is not limited to the above-described embodiment alone, and various modifications are made without departing from the gist of the present invention. Implementation is possible.

  According to the above-described embodiment, it is possible to adjust not only a scanning curve of a quadratic curve but also a scanning line of a higher-order component higher than a cubic function, so that a scanning optical system with a small image distortion Can be provided. In addition, since the accuracy of the receiving portion of the scanning lens can be relaxed, it is possible to reduce costs and save resources by improving yield.

  Further, according to the above-described embodiment, it is possible to provide an optical scanning device with a small image distortion by reducing the scanning line bending.

  Further, according to the above-described embodiment, it is possible to reduce the scanning line bending of each scanning optical system in the tandem optical system including a plurality of scanning optical systems, and thus it is possible to provide an optical scanning device with a small color shift. It becomes.

  Further, according to the above-described embodiment, an image forming apparatus capable of outputting a high-quality image is realized by using an optical scanning device that can reduce the bending of a scanning line. It is possible to provide an image forming apparatus without deviation.

It is the figure which showed schematic structure of the scanning optical system which concerns on embodiment of this invention. It is a figure for demonstrating the prior art regarding adjustment of a scanning line curve. It is a figure showing the generation | occurrence | production state and adjustment result of the scanning line bending in embodiment of this invention. It is a figure showing the generation | occurrence | production state and adjustment result of the scanning line bending in embodiment of this invention. It is the figure which showed the structure of the folding mirror in embodiment of this invention. It is a figure showing the simulation result of adjustment of scanning line bending in the embodiment of the present invention. It is the figure which showed the structure of the scanning lens vicinity in embodiment of this invention. 1 is a diagram illustrating a schematic configuration of an optical scanning device according to an embodiment of the present invention. 1 is a diagram illustrating a schematic configuration of an optical scanning device according to an embodiment of the present invention. 1 is a diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source 2 Coupling lens 3 Cylindrical lens 4 Optical deflector 5,6 Scanning lens 7 Scanned surface 21 Sheet metal 22,23,24,25 Leaf spring 26 Protrusion part 32 Stepping motor 51 Housing 100,101,102 Folding mirror 110, 120 Both ends 130 Central part 140,150 Intermediate part 160 Rotating shaft

Claims (6)

An optical deflector for deflecting a light beam from a light source, at least one scanning lens for condensing the optical deflector in the vicinity of a scanned surface, and at least one sheet provided between the deflector and the scanned surface A folding optical system , and a scanning optical system comprising:
The scanning lens has secondary component correction means for correcting a quadratic function component of scanning line bending,
The folded mirror is to have a high-order component correction means for correcting the high-order function ingredients and quartic function or higher-order functional components of the third-order function of the bending of the scanning line,
The high-order component correction means fixes both ends and substantially the center of the folding mirror, and is an intermediate part located between the both ends and the substantially center, which is a movable part other than the both ends and the substantially center. A scanning optical system characterized by twisting about a straight line intersecting a scanning plane and the folding mirror as a rotation axis .   The scanning optical system according to claim 1, wherein the secondary component correction unit presses a substantially central portion in a longitudinal direction of the scanning lens in a direction substantially perpendicular to a scanning plane. The scanning lens according to claim 1 or 2 characterized in that it has a scanning line inclination adjusting means for adjusting the inclination scan lines by rotating the scanning lens as a fulcrum lower surface or upper surface of the substantially central portion in the longitudinal direction Scanning optical system. Optical scanning apparatus characterized by having a scanning optical system according to any one of claims 1 to 3. The optical scanning device according to claim 4 , comprising a plurality of scanning optical systems. Image forming apparatus characterized by mounting the optical scanning device according to claim 4 or 5.

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