Optical scanner and image forming apparatus

Abstract

To provide an optical scanner that can arrange respective light sources so as to make the lengths of optical paths from the light sources to a rotary polygon mirror equal to each other.SOLUTION: An optical scanner has a first expander lens 83b that spreads beams LB radiated from a plurality of laser diodes 81 in a main scanning direction S. The beams LB radiated from the plurality of laser diodes 81 are incident on the single first expander lens 83b. The plurality of laser diodes 81 are arranged so that, in the main scanning direction S, optical paths of the beams from the plurality of laser diodes 81 to a polygon mirror 86 (rotary polygon mirror) overlap each other when seen from a direction along a rotation axis of the polygon mirror 86.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present disclosure relates to an optical scanning device and an image forming apparatus that cause beams emitted from a plurality of light sources to be incident on a polygon mirror. [Background technology]

[0002] Conventionally, image forming devices such as digital copiers, laser printers, and facsimiles use optical scanning devices that scan a laser beam. When forming an image using an image forming device, a photoconductor is charged by a charging device, and then writing is performed according to image information using an optical scanning device to form an electrostatic latent image on the photoconductor. The electrostatic latent image on the photoconductor is then visualized using toner supplied from a developing device. The toner image visualized on the photoconductor is transferred to paper by a transfer device, and then fixed to the paper by a fixing device, thereby obtaining a desired image.

[0003] Laser diodes serving as light sources for optical scanning devices are arranged close to each other in the height direction and arranged side by side with an inclination (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2012-8423 A Summary of the Invention [Problem to be solved by the invention]

[0005] In conventional optical scanning devices, multiple laser diodes are arranged diagonally side by side to place each laser diode close to the other in the height direction, taking into account optical performance such as beam size. Therefore, the positions of the multiple laser diodes are shifted in the main scanning direction of the optical scanning device, and the optical paths are different for each, which creates the problem of the need for multiple folding mirrors and lenses.

[0006] The present disclosure has been made to solve the above-mentioned problems, and aims to provide an optical scanning device and an image forming device in which the optical path lengths from each light source to a rotating polygon mirror can be arranged to be equal. [Means for solving the problem]

[0007] The optical scanning device disclosed herein is an optical scanning device that causes beams emitted from multiple light sources to be incident on a rotating polygon mirror, and is characterized in that it has a first expander lens that expands the beams emitted from the multiple light sources in a main scanning direction, and the beams emitted from the multiple light sources are incident on a single first expander lens, and the multiple light sources are arranged so that, in the main scanning direction, the optical paths of each beam from the multiple light sources to the rotating polygon mirror overlap when viewed from a direction along the rotation axis of the rotating polygon mirror.

[0008] In the optical scanning device according to the present disclosure, the plurality of light sources may be arranged linearly along a sub-scanning direction perpendicular to the main scanning direction.

[0009] The optical scanning device according to the present disclosure may be configured to include a cylindrical lens that changes the angle of incidence on the rotating polygon mirror in a sub-scanning direction perpendicular to the main scanning direction.

[0010] In the optical scanning device according to the present disclosure, the cylindrical lens may be integral with the first expander lens.

[0011] In the optical scanning device according to the present disclosure, the multiple light sources may be arranged so that the angles of incidence of each beam emitted from the multiple light sources on the rotating polygon mirror are asymmetric in the sub-scanning direction.

[0012] In the optical scanning device according to the present disclosure, the optical path from the multiple light sources to the rotating polygon mirror may be configured such that a second expander lens for collimating the beam is disposed between the first expander lens and the rotating polygon mirror.

[0013] The optical scanning device according to the present disclosure may further include a housing in which the light source is attached, the housing having an opening for narrowing down the beam emitted from the light source.

[0014] The image forming apparatus according to the present disclosure is characterized by including the optical scanning device according to the present disclosure. Effect of the Invention

[0015] According to the present disclosure, the optical path lengths from each light source to the rotating polygon mirror are equal and the focal points are aligned, so that a single first expander lens can be used, thereby saving space and reducing costs. [Brief description of the drawings]

[0016] [Figure 1] 1 is a schematic side view of an image forming apparatus according to an embodiment of the present disclosure. [Diagram 2] 1 is a perspective view illustrating an optical scanning device according to an embodiment of the present disclosure. [Diagram 3] 1 is a plan view illustrating an optical scanning device according to an embodiment of the present disclosure. [Figure 4] 4 is an enlarged side view showing an attachment portion of the laser diode in the housing; FIG. [Diagram 5] FIG. 4 is an enlarged perspective view showing the vicinity of an aperture forming portion. [Figure 6] FIG. 2 is an enlarged cross-sectional view showing the vicinity of an aperture forming portion as viewed from the front. [Figure 7] FIG. 2 is a schematic perspective view showing the positional relationship of optical components in an optical scanning device. [Figure 8] FIG. 2 is a schematic plan view showing the positional relationship of optical components in the optical scanning device. [Figure 9]FIG. 4 is a schematic explanatory diagram showing a part of the optical path of a beam in the main scanning direction. [Figure 10] FIG. 4 is a schematic explanatory diagram showing a part of the optical path of a beam in the sub-scanning direction. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, an image forming apparatus according to an embodiment of the present disclosure will be described with reference to the drawings.

[0018] FIG. 1 is a schematic side view of an image forming apparatus according to an embodiment of the present disclosure.

[0019] Image forming device 100 is a multifunction device having a scanner function, a copy function, a printer function, a facsimile function, etc., and transmits an image of an original document read by an image reading device to the outside (corresponding to the scanner function), and also forms an image of the read original document or an image received from the outside on paper in color or monochrome (corresponding to the copy function, printer function, and facsimile function).

[0020] An original transport device 50 (ADF) is provided above the image reading unit 41 and is supported so as to be freely opened and closed relative to the image reading unit 41. When the original transport device 50 is opened, an original placement table 44 above the image reading unit 41 is opened, allowing an original to be placed manually. The original transport device 50 automatically transports the placed original onto the image reading unit 41. The image reading unit 41 reads the placed original or the original transported from the original transport device 50 to generate image data.

[0021] The image forming apparatus 100 includes an optical scanning device 1, a developing device 2, a photosensitive drum 3, a drum cleaning device 4, a charger 5, an intermediate transfer belt 7, a fixing unit 12, a paper transport path Sm, a paper feed cassette 10, a loading tray 15, and the like.

[0022] Image forming apparatus 100 handles image data corresponding to color images using the colors black (K), cyan (C), magenta (M), and yellow (Y), or monochrome images using a single color (e.g., black). Image forming apparatus 100 is provided with four developing devices 2, four photoconductor drums 3, four drum cleaning devices 4, and four chargers 5 for forming four types of toner images, each corresponding to black, cyan, magenta, and yellow, constituting four image stations Pa, Pb, Pc, and Pd.

[0023] The drum cleaning device 4 removes and collects residual toner on the surface of the photosensitive drum 3. The charger 5 uniformly charges the surface of the photosensitive drum 3 to a predetermined potential. The optical scanning device 1 exposes the surface of the photosensitive drum 3 to light to form an electrostatic latent image. The developing device 2 develops the electrostatic latent image on the surface of the photosensitive drum 3 to form a toner image on the surface of the photosensitive drum 3. Through the above-mentioned series of operations, a toner image of each color is formed on the surface of each photosensitive drum 3. The detailed structure of the optical scanning device 1 will be described later with reference to FIG. 2 and FIG. 3.

[0024] A transfer belt device 8 is provided above the photosensitive drums 3, and intermediate transfer rollers 6 are arranged with an intermediate transfer belt 7 interposed therebetween. The intermediate transfer belt 7 is stretched around a transfer drive roller 21 and a transfer driven roller 22, and moves in a circular motion in the direction of arrow C. Residual toner is removed and collected by a belt cleaning device 9, and the toner images of each color formed on the surface of each photosensitive drum 3 are transferred in sequence and superimposed on top of each other to form a color toner image on the surface of the intermediate transfer belt 7.

[0025] A nip area is formed between the transfer roller 11a of the secondary transfer unit 11 and the intermediate transfer belt 7, and the paper conveyed through the paper conveying path Sm is sandwiched in the nip area and conveyed. When the paper passes through the nip area, the toner image on the surface of the intermediate transfer belt 7 is transferred to the paper, and the paper is conveyed to the fixing unit 12.

[0026] The fixing unit 12 includes a fixing roller 31 and a pressure roller 32 that rotate while sandwiching the paper. The fixing unit 12 sandwiches the paper, onto which the toner image has been transferred, between the fixing roller 31 and the pressure roller 32 and applies heat and pressure to fix the toner image to the paper.

[0027] The paper feed cassette 10 is a cassette for storing paper to be used for image formation, and is provided below the optical scanning device 1. The paper is pulled out from the paper feed cassette 10 by a paper pickup roller 16, transported through a paper transport path Sm, passed through a secondary transfer unit 11 and a fixing unit 12, and discharged to a stack tray 15 via a paper discharge roller 17. On the paper transport path Sm, there are arranged a paper registration roller 14 that temporarily stops the paper, aligns the leading edge of the paper, and starts transporting the paper in accordance with the transfer timing of the color toner image in the nip area between the intermediate transfer belt 7 and the transfer roller 11a, a transport roller 13 that promotes the transport of the paper, and a paper discharge roller 17.

[0028] When an image is to be formed on the back side of the paper in addition to the front side, the paper is transported in the opposite direction from the paper discharge rollers 17 to the paper inversion path Sr. In the paper inversion path Sr, the paper is inverted by the inversion rollers 18 and guided again to the paper registration rollers 14. Thereafter, an image is formed on the back side in the same manner as on the front side, and the paper is conveyed to the stacking tray 15.

[0029] FIG. 2 is a perspective view showing an optical scanning device according to an embodiment of the present disclosure, and FIG. 3 is a plan view showing the optical scanning device according to the embodiment of the present disclosure.

[0030] The optical scanning device 1 according to the embodiment of the present disclosure includes a rectangular housing 60, and optical components are attached to each part of the housing 60. In addition, in Figs. 2 and 3, in consideration of ease of viewing the drawings, some members such as the top surface of the housing 60 are removed so that the inside of the housing 60 can be seen. For the sake of explanation below, the direction along one side surface (for example, the mounting side surface 61) of the housing 60 may be referred to as the width direction X, the direction along the side surface adjacent to the mounting side surface 61 may be referred to as the length direction Y, and the direction perpendicular to the width direction X and the length direction Y may be referred to as the height direction Z. The above-mentioned width direction X is also the main scanning direction S of the optical scanning device 1, the length direction Y is also the direction in which a beam is emitted from the light source, and the height direction Z is also the sub-scanning direction H of the optical scanning device 1.

[0031] FIG. 4 is an enlarged side view showing an attachment portion of the laser diode in the housing.

[0032] A plurality of laser diodes 81 (an example of a light source) are attached to the mounting side surface 61 of the housing 60. Fig. 4 shows an enlarged view of the mounting side surface 61 of the housing 60 and the vicinity of the mounting locations of the laser diodes 81. In this embodiment, four laser diodes 81 are attached to the housing 60. The four laser diodes 81 (first diode 81a to fourth diode 81d) are arranged in a straight line aligned in the height direction Z.

[0033] In addition to the laser diode 81, optical components such as a collimator lens 82, an integrated lens 83 (cylindrical lens 83a and first expander lens 83b), a reflecting mirror 84, a second expander lens 85, a polygon mirror 86 (rotating polygonal mirror), and an fθ lens 87 are attached to the housing 60. However, the housing 60 may be equipped with various components such as mirrors, lenses, and sensors. The relationship between the beam LB emitted from the laser diode 81 and the optical components will be described with reference to FIGS. 7 and 8, which will be described later.

[0034] An aperture forming portion 62 is provided in the housing 60 near the portion where the collimator lens 82 is attached.

[0035] 5 is an enlarged perspective view showing the vicinity of the aperture forming portion, and FIG. 6 is an enlarged cross-sectional view taken along the line AA of FIG. 5 and showing the vicinity of the aperture forming portion.

[0036] The aperture forming section 62 is a wall surface that blocks the gap between the collimator lens 82 and the integrated lens 83. The aperture forming section 62 has an aperture 62a (opening) that opens a portion facing the collimator lens 82. The aperture 62a has a function of narrowing down the beams emitted from the four laser diodes 81 (the first diode 81a to the fourth diode 81d). When passing through the aperture 62a, the beam emitted from the collimator lens 82 is shaped into a shape corresponding to the aperture 62a. In this way, by providing the aperture 62a in the housing 60 itself, the space for mounting the aperture 62a can be saved. The number and position of the apertures 62a can be adjusted according to the laser diodes 81.

[0037] Fig. 7 is a schematic perspective view showing the positional relationship of optical components in an optical scanning device, and Fig. 8 is a schematic plan view showing the positional relationship of optical components in an optical scanning device. In Fig. 7 and Fig. 8, some of the optical components in the optical scanning device 1 are extracted and shown for ease of viewing.

[0038] As described above, optical components such as a laser diode 81 (first diode 81a to fourth diode 81d), a collimator lens 82, an integrated lens 83, a reflecting mirror 84, a second expander lens 85, a polygon mirror 86, and an fθ lens 87 are attached to the housing 60 of the optical scanning device 1.

[0039] In FIG. 7, a part of the beam LB emitted from the laser diode 81 (particularly the second diode 81b) is indicated by a dashed line. Although omitted in FIG. 7, the beam LB is also emitted from the laser diodes 81 other than the second diode 81b. The main scanning direction S and the sub-scanning direction H given to the beam LB are the directions in which the beam LB is scanned and correspond to the directions in which the light spreads. In the optical path of the beam LB, between the laser diode 81 and the reflecting mirror 84, the main scanning direction S is parallel to the width direction X, and the sub-scanning direction H is parallel to the height direction Z. For the sake of explanation, in the optical path of the beam LB, the part from the laser diode 81 to the polygon mirror 86 may be referred to as the incident system, and the part from the polygon mirror 86 to the scanned surface (for example, the photosensitive drum 3) may be referred to as the emission system.

[0040] Four collimator lenses 82 are provided corresponding to the four laser diodes 81, and are disposed on the optical path of the beam LB emitted from the laser diodes 81.

[0041] The integrated lens 83 is disposed on the optical path of the beam LB emitted from the collimator lens 82. In this embodiment, one integrated lens 83 is provided corresponding to the four laser diodes 81. Specifically, the integrated lens 83 is a vertically elongated lens that is long in the height direction Z (sub-scanning direction H) in accordance with the four laser diodes 81 arranged side by side in the height direction Z, and is configured so that all of the beams LB emitted from the four laser diodes 81 are incident on the integrated lens 83.

[0042] In this embodiment, the integrated lens 83 is a lens having different curvatures in the directions of the incident surface and the exit surface. In this way, by consolidating two lenses (the cylindrical lens 83a and the first expander lens 83b), the device can be made more compact.

[0043] Specifically, the entrance surface of the integrated lens 83 is a cylindrical lens 83a, which acts to narrow the incident beam LB in the sub-scanning direction H. Furthermore, the cylindrical lens 83a adjusts the exit direction (irradiation angle) of the passing beam LB in the sub-scanning direction H. The four beams LB that have passed through the cylindrical lens 83a change their exit direction so that the beams LB converge to each other in the sub-scanning direction H. When the four beams LB reach the polygon mirror 86, they are most convergent to each other in the sub-scanning direction H, and after passing through the polygon mirror 86, the beams LB diffuse to each other in the sub-scanning direction H.

[0044] The exit surface of the integrated lens 83 is a first expander lens 83b, which acts to expand the irradiation range of the incident beam LB in the main scanning direction S (width direction X).

[0045] In the present embodiment, an integrated lens 83 in which the cylindrical lens 83a and the first expander lens 83b are integrated is used, but the present invention is not limited to this, and each of them may be independent, and a configuration having two lenses may be used. In this case, too, the cylindrical lens 83a may be arranged on the upstream side of the optical path of the beam LB, and the first expander lens 83b may be arranged on the downstream side.

[0046] The reflecting mirror 84 is disposed on the optical path of the beam LB emitted from the integrated lens 83 , and guides the reflected beam LB so that it passes through a curved lens 85 and enters a polygon mirror 86 .

[0047] The second expander lens 85 is disposed on the optical path between the reflecting mirror 84 and the polygon mirror 86, and acts to narrow the irradiation range of the incident beam LB in the main scanning direction S. The second expander lens 85 has a curvature corresponding to the first expander lens 83b, and collimates the incident beam LB. In other words, the irradiation range of the beam LB in the main scanning direction S does not change after passing through the second expander lens 85.

[0048] The polygon mirror 86 is, for example, a polygonal mirror having multiple faces and has a rotation axis that rotates by a drive unit such as a motor, and reflects the incident beam LB while rotating, causing the beam LB to scan the surface of the photosensitive drum 3.

[0049] The fθ lens 87 is provided at a position opposite to the polygon mirror 86, and the beam LB emitted from the polygon mirror 86 is incident on the fθ lens 87. Although not shown, optical components such as lenses and mirrors may be provided in the optical path beyond the fθ lens 87, and the beam LB may scan the surface of the photosensitive drum 3 via these components.

[0050] Next, the behavior of the beam LB in the optical path of the incident system will be described with reference to FIGS.

[0051] Fig. 9 is a schematic explanatory diagram showing a part of the optical path of the beam in the main scanning direction S, and Fig. 10 is a schematic explanatory diagram showing a part of the optical path of the beam in the sub-scanning direction H. Note that the reflection mirror 84 is omitted because it has no effect on the optical path length and irradiation range of the beam LB.

[0052] 9 shows a state seen from a direction along the rotation axis of the polygon mirror 86. As shown in FIG. 9, the multiple laser diodes 81 are arranged so that the optical paths of the beams from the multiple laser diodes 81 to the polygon mirror 86 overlap in the main scanning direction S. In this configuration, the optical path lengths from the laser diodes 81 to the polygon mirror 86 are equal and the focal points coincide, so that one first expander lens 83b can be used, thereby saving space and reducing costs. As described above, the multiple laser diodes 81 are arranged linearly along the sub-scanning direction H, so that the optical paths from the laser diodes 81 can easily overlap.

[0053] 10 is a straight line extending from the point where the beam LB is incident on the polygon mirror 86 along the sub-scanning direction H. In this embodiment, the first diode 81a and the second diode 81b are located above the reference line KL, and the third diode 81c and the fourth diode 81d are located below the reference line KL. Looking more closely, the first diode 81a and the second diode 81b are located closer to the reference line KL than the third diode 81c and the fourth diode 81d, and the reference line KL passes between the second diode 81b and the third diode 81c.

[0054] In addition, regarding the beam LB emitted from the first diode 81a to the fourth diode 81d, looking at the angle of incidence (the angle between the beam LB and the reference line KL) with respect to the polygon mirror 86 in the sub-scanning direction H, the angle of incidence (first angle of incidence θ1) of the beam LB in the first diode 81a is smaller than the angle of incidence (fourth angle of incidence θ4) of the beam LB in the fourth diode 81d, and the angle of incidence (second angle of incidence θ2) of the beam LB in the second diode 81b is smaller than the angle of incidence (third angle of incidence θ3) of the beam LB in the third diode 81c. In other words, the first diode 81a and the second diode 81b, and the third diode 81c and the fourth diode 81d are arranged so that the angles of incidence of each beam emitted from the multiple laser diodes 81 to the polygon mirror 86 in the sub-scanning direction H are asymmetric. In this way, by arranging the multiple laser diodes 81 asymmetrically, it is possible to prevent the reflected light (return light) from the polygon mirror 86 from entering the laser diode 81.

[0055] Conventionally, in order to improve optical performance (beam size, etc.), multiple laser diodes were arranged side-by-side at an angle because each laser diode had to be placed close to each other in the height direction Z. However, in order to adopt an overfill optical system in an optical scanning device, it is necessary to incorporate an expander lens that widens the beam into the incident system.

[0056] Therefore, if the conventional arrangement of multiple laser diodes arranged side by side is adopted for the optical scanning device, the optical path length from each laser diode to the polygon mirror surface differs for each color beam, so in order to obtain the desired optical performance, it is necessary to place an expander lens (four lenses) on the beam path of each laser diode, which increases costs. Also, if the beam paths of each laser diode are to be overlapped in the main scanning direction S, a reflecting mirror or the like is required.

[0057] On the other hand, when the laser diodes are arranged in a straight line in the height direction as in this embodiment, the optical path length from each laser diode to the polygon mirror surface becomes equal, and only one expander lens is required, which can reduce costs. Also, in this embodiment, an overfill optical system may be adopted for the optical scanning device 1.

[0058] It should be noted that the embodiments disclosed herein are illustrative in all respects and are not intended to provide a basis for a restrictive interpretation. Therefore, the technical scope of the present disclosure is not interpreted solely by the above-described embodiments, but is defined based on the claims. In addition, the present disclosure includes all modifications within the scope and meaning equivalent to the claims. [Explanation of symbols]

[0059] 1 Optical scanning device 60 Case 62 Aperture forming section 62a Aperture (an example of an opening) 81 Laser diode (example of light source) 82 Collimator lens 83 Integrated Lens 83a Cylindrical Lens 83b 1st expander lens 84 Reflective Mirror 85 2nd expander lens 86 Polygon mirror (an example of a rotating polygonal mirror) 87 fθ lens 100 Image forming device S Main scanning direction H Sub-scanning direction

Claims

1. An optical scanning device that causes beams emitted from a plurality of light sources to be incident on a rotating polygon mirror, a first expander lens that expands the beams emitted from the plurality of light sources in a main scanning direction; The beams emitted from the multiple light sources are incident on the single first expander lens, The plurality of light sources are arranged such that optical paths of the beams from the plurality of light sources to the rotating polygon mirror overlap in the main scanning direction when viewed from a direction along the rotation axis of the rotating polygon mirror. An optical scanning device comprising:

2. 2. The optical scanning device according to claim 1, The plurality of light sources are arranged linearly along a sub-scanning direction perpendicular to the main scanning direction. An optical scanning device comprising:

3. 2. The optical scanning device according to claim 1, A cylindrical lens is provided for changing the angle of incidence of the rotating polygon mirror in a sub-scanning direction perpendicular to the main scanning direction. An optical scanning device comprising:

4. 4. The optical scanning device according to claim 3, The cylindrical lens is integrated with the first expander lens. An optical scanning device comprising:

5. 4. The optical scanning device according to claim 3, The plurality of light sources are arranged such that the angles of incidence of the beams emitted from the plurality of light sources on the rotary polygon mirror are asymmetric in the sub-scanning direction. An optical scanning device comprising:

6. 2. The optical scanning device according to claim 1, A second expander lens for collimating beams is disposed between the first expander lens and the rotating polygon mirror on the optical path from the plurality of light sources to the rotating polygon mirror. An optical scanning device comprising:

7. 2. The optical scanning device according to claim 1, a housing in which the light source is mounted; The housing has an opening for narrowing down the beam emitted from the light source. An optical scanning device comprising:

8. An image forming apparatus comprising the optical scanning device according to claim 1.

Images