Lens mirror array

Abstract

To provide a lens mirror array capable of providing a wide depth-of-field performance.SOLUTION: A lens mirror array according to an embodiment comprises multiple optical elements arranged in a main scanning direction. Each optical element has an incident lens surface for transmitting and converging incident light, an upstream mirror surface for reflecting the light entering via the incident lens surface, a downstream mirror surface for reflecting the light reflected by the upstream mirror surface, and an exit lens surface for transmitting and converging the light reflected by the downstream mirror surface. The incident lens surface temporarily converges the incident light in the main scanning direction between the downstream mirror surface to the exit lens surface.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] Embodiments of the present invention relate to a lens mirror array used, for example, in a scanner of an image forming apparatus installed in a workplace.

Background Art

[0002] For example, a scanner of a copying machine has a lens and mirror integrated array (hereinafter referred to as a lens mirror array) for refracting and reflecting light reflected from an original surface and condensing it onto a CCD sensor or the like. The lens mirror array has, for example, a plurality of optical elements arranged in the main scanning direction. Each optical element has an incident-side lens surface that transmits and converges incident light, an upstream-side mirror surface that reflects light incident through the incident-side lens surface, a downstream-side mirror surface that reflects light reflected by the upstream-side mirror surface, and an exit-side lens surface that transmits and converges light reflected by the downstream-side mirror surface.

[0003] In such a lens mirror array, light incident from the incident-side lens surface converges once in the main scanning direction between the upstream-side mirror surface and the downstream-side mirror surface, spreads again in the main scanning direction, and is reflected by the downstream-side mirror surface. The reflected light passes through the exit-side lens surface and forms an image on the image plane.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in such a lens mirror array, the generation of stray light is significant. In order to reduce the stray light to an acceptable level, it is necessary to increase the lens pitch and separate adjacent optical elements. Therefore, it is difficult to reduce the lens pitch, and as a result, it is difficult to widen the depth of field performance.

[0006] The problem to be solved by the present invention is to provide a lens mirror array capable of obtaining a wide depth of field performance.

Means for Solving the Problem

[0007] The lens mirror array according to the embodiment has a plurality of optical elements arranged in the main scanning direction. Each optical element has an incident-side lens surface that transmits and converges incident light, an upstream-side mirror surface that reflects the light incident through the incident-side lens surface, a downstream-side mirror surface that reflects the light reflected by the upstream-side mirror surface, and an exit-side lens surface that transmits and converges the light reflected by the downstream-side mirror surface. The incident-side lens surface converges the incident light once in the main scanning direction between the downstream-side mirror surface and the exit-side lens surface.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

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Figure 7

Figure 8

Figure 9

Figure 10

BEST MODE FOR CARRYING OUT THE INVENTION

[0009] Hereinafter, embodiments will be described with reference to the drawings. Note that the scales of the respective parts in the following drawings may be appropriately changed. Also, the following drawings used in the description of the embodiments may show a part of the configuration omitted for easy understanding of the description.

[0010] Also, in each figure, an XYZ coordinate system is set as follows. The vertical direction is the Z direction. The moving direction of the reading module 70 of the scanner 20 described later is the Y direction. The direction perpendicular to the Y direction and the Z direction is the X direction. The X direction is the main scanning direction. The Y direction is the sub-scanning direction.

[0011] (Image forming apparatus) First, with reference to FIG. 1, an image forming apparatus 100 according to an embodiment will be described. The image forming apparatus 100 according to the embodiment specifically includes a scanner 20 having a reading module 70 having a lens mirror array 90 (see FIG. 3) according to the embodiment. FIG. 1 is a schematic diagram showing the image forming apparatus 100 according to the embodiment.

[0012] The image forming apparatus 100 according to the embodiment is, for example, an MFP (multifunction peripheral). The image forming apparatus 100 has functions such as a printing function, a scanning function, and a copying function. The printing function is a function of forming a toner image on a sheet P. The scanning function is a function of reading an image from a document or the like on which an image is formed. The copying function is a function of printing, for example, an image read from a document or the like using the scanning function, onto the sheet P using the printing function.

[0013] The image forming apparatus 100 includes a printer 10, a scanner 20, and an operation panel 30.

[0014] The printer 10 includes a plurality of paper feed cassettes 11, a manual feed tray 12, and a plurality of paper feed rollers 13. The paper feed cassette 11 stores the sheet P used for printing. The manual feed tray 12 is for manually inserting the sheet P. The paper feed roller 13 selectively takes out the sheet P from either the paper feed cassette 11 or the manual feed tray 12 by rotating.

[0015] The printer 10 includes four toner cartridges 141, 142, 143, 144, four image forming units 151, 152, 153, 154, an optical scanning device 16, a transfer belt 17, a secondary transfer roller 18, and a fixing unit 19.

[0016] The toner cartridges 141 to 144 each contain toner to be supplied to the image forming units 151 to 154. The toner cartridge 141 contains yellow (Y) toner. The toner cartridge 142 contains magenta (M) toner. The toner cartridge 143 contains cyan (C) toner. The toner cartridge 144 contains black (K) toner. The combination of toner colors is not limited to YMCK and may be other combinations of colors.

[0017] The image forming units 151 to 154 each receive the supply of toner from the toner cartridges 141 to 144 and form toner images of different colors. The image forming unit 151 forms a yellow (Y) toner image. The image forming unit 152 forms a magenta (M) toner image. The image forming unit 153 forms a cyan (C) toner image. The image forming unit 154 forms a black (K) toner image.

[0018] (Image forming unit) The image forming units 151 to 154 have the same configuration except for the difference in toner. Therefore, here, with reference to FIG. 2, the image forming unit 151 for yellow will be described as a representative, and the descriptions of the image forming units 152 to 154 for other colors will be omitted. FIG. 2 is a schematic diagram showing the image forming unit 151 of the image forming apparatus 100.

[0019] The image forming unit 151 for yellow includes a photosensitive drum 41, a charging device 42, a developing device 43, a primary transfer roller 44, a cleaner 45, and a charge elimination lamp 46.

[0020] The photosensitive drum 41 has a surface that receives the light beam BY irradiated from the optical scanning device 16. The optical scanning device 16 forms an electrostatic latent image on the surface of the photosensitive drum 41. The charging device 42 charges the surface of the photosensitive drum 41 with positive charges. The developing device 43 develops the electrostatic latent image on the surface of the photosensitive drum 41 using the yellow toner D supplied from the toner cartridge 141. That is, the developing device 43 forms a yellow toner image on the surface of the photosensitive drum 41.

[0021] Also, the image forming unit 151 includes a primary transfer roller 44 at a position facing the photosensitive drum 41 with the transfer belt 17 interposed therebetween. The primary transfer roller 44 generates a transfer voltage between itself and the photosensitive drum 41. Thereby, the primary transfer roller 44 transfers (primary transfer) the yellow toner image on the surface of the photosensitive drum 41 to the surface of the transfer belt 17 in contact with the photosensitive drum 41.

[0022] The cleaner 45 removes the toner remaining on the surface of the photoreceptor drum 41. The charge-removing lamp 46 removes the charges remaining on the surface of the photoreceptor drum 41.

[0023] The optical scanning device 16 irradiates the surfaces of the photoreceptor drums 41 of the image forming units 151, 152, 153, and 154 with light beams BY, BM, BC, and BK, respectively, according to the input image data. The light beams BY, BM, BC, and BK are respectively based on the image data of each color obtained by color-separating the image data into Y, M, C, and K colors.

[0024] The optical scanning device 16 emits the light beam BY according to the Y-component image data to form a yellow electrostatic latent image on the surface of the photoreceptor drum 41 of the image forming unit 151. Similarly, the optical scanning device 16 emits the light beams BM, BC, and BK according to the M, C, and K-component image data to form electrostatic latent images for each color on the surfaces of the photoreceptor drums 41 of the image forming units 152, 153, and 154.

[0025] Note that the image data input to the optical scanning device 16 is, for example, image data read from a document or the like by the scanner 20. Alternatively, the image data input to the optical scanning device 16 is image data transmitted from a device different from the image forming apparatus 100 to the image forming apparatus 100.

[0026] The transfer belt 17 is stretched in an endless shape and rotates by rotating the drive roller 171 around which the transfer belt 17 is wound. By rotating, the transfer belt 17 conveys the toner images of each color formed in an overlapping manner on the surface of the transfer belt 17 by the image forming units 151 to 154 to the transfer area facing the secondary transfer roller 18.

[0027] The secondary transfer roller 18 faces the drive roller 171 with the transfer belt 17 interposed therebetween. The secondary transfer roller 18 transfers (secondary transfer) the toner image formed on the transfer belt 17 onto the paper P passing between the secondary transfer roller 18.

[0028] The fixing unit 19 heats and presses the paper P. The fixing unit 19 includes a heating roller 191 and a pressure roller 192 that face each other with the conveyance path of the paper P therebetween. The heating roller 191 includes a heat source such as a heater. The heating roller 191 heated by the heat source heats the paper P. The pressure roller 192 presses the paper P passing between the pressure roller 192 and the heating roller 191. Therefore, the fixing unit 19 fixes the toner image transferred onto the paper P.

[0029] In addition, the printer 10 includes a duplex unit 50 and a paper discharge tray 60. The duplex unit 50 makes the paper P printable on the back side. The duplex unit 50 reverses the front and back of the paper P by switching it back and feeds it into the transfer area between the transfer belt 17 and the secondary transfer roller 18. The paper discharge tray 60 receives the paper P discharged after printing is completed.

[0030] The scanner 20 reads an image from a document or the like. The scanner 20 includes a reading module 70 and a document feeder 80.

[0031] The reading module 70 irradiates illumination light onto the surface of a document having an image to be read (hereinafter referred to as the document surface), and receives the reflected light with an image sensor 76 (see FIG. 3) and converts it into a digital signal. Thereby, the reading module 70 reads an image from the document surface. The reading module 70 includes a lens mirror array 90 (see FIG. 3) that guides the reflected light from the document to the image sensor 76.

[0032] The document feeder 80 is, for example, an ADF (auto document feeder) or the like. The document feeder 80 successively conveys the documents placed on the document tray 81 through the document glass 82. The reading module 70 reads an image from the document conveyed to the document glass 82. The document feeder 80 may include another reading module for reading an image from the back side of the document.

[0033] The operation panel 30 is a man-machine interface that performs input and output between the image forming apparatus 100 and the operator of the image forming apparatus 100. The operation panel 30 includes, for example, a touch panel 31 and an input device 32.

[0034] The touch panel 31 is, for example, a laminate of a display such as a liquid crystal display or an organic EL display and a pointing device by touch input. The display of the touch panel 31 displays a screen for notifying various information to the operator of the image forming apparatus 100. Further, the touch panel 31 receives a touch operation by the operator.

[0035] The input device 32 receives an operation by the operator of the image forming apparatus 100. The input device 32 is, for example, a keyboard, a keypad, or a touch pad.

[0036] (Reading module) Next, with reference to FIG. 3, the reading module 70 of the scanner 20 of the image forming apparatus 100 will be described. FIG. 3 is a cross-sectional view showing the reading module 70 of the scanner 20 of the image forming apparatus 100.

[0037] As shown in FIG. 3, the reading module 70 includes a lens mirror array 90 according to the embodiment, two reflecting plates 72, two light guides 74, an image sensor 76, and a holder 78. The holder 78 positions and holds the lens mirror array 90, the reflecting plate 72, the light guide 74, and the image sensor 76 (substrate 75 on which the image sensor 76 is mounted).

[0038] The lens mirror array 90 forms an erect image of the image on the document surface on the image sensor 76. Therefore, by moving the reading module 70 along the document glass 82 in the sub-scanning direction (Y direction), the entire image on the document surface can be read by the image sensor 76.

[0039] The image sensor 76 has an elongated structure extending in the main scanning direction. The image sensor 76 is a line sensor in which a plurality of imaging elements that convert light into electrical signals are arranged linearly in the main scanning direction. The image sensor 76 is one or more line sensors. The image sensor 76 can be composed of, for example, a Charge Coupled Device (CCD), a Complimentary Metal Oxide Semiconductor (CMOS), or other imaging elements.

[0040] The holder 78 has an elongated structure extending in the main scanning direction. The holder 78 can be formed by integrally molding resin using a mold. The holder 78 has a pair of side walls 781 arranged along the main scanning direction, a pair of end walls 782 (only the back side is shown in FIG. 3) arranged at both longitudinal ends of the side walls 781, and a partition wall 783 connecting the inner surfaces of the middle portions in the vertical direction of the pair of side walls 781 and the inner surfaces of the middle portions in the vertical direction of the pair of end walls 782. In the middle portion of the partition wall 783 in the sub-scanning direction (Y direction), there is a bulging portion 784 bulging upward. The bulging portion 784 has an elongated structure extending in the main scanning direction.

[0041] The bulging portion 784 of the holder 78 has a rectangular slit-shaped aperture 785 extending in the main scanning direction at approximately the center in the sub-scanning direction. The aperture 785 allows the reflected light from the document surface to pass through, narrows the width of the reflected light in the sub-scanning direction, and guides it to the lens mirror array 90. The holder 78 holds the lens mirror array 90 inside the bulging portion 784, that is, below the aperture 785 in the drawing. The width of the aperture 785 in the sub-scanning direction is smaller than the width at which the reflected light from the document passing through the aperture 785 is incident on the plurality of incident-side lens surfaces 92 (see FIG. 4) of the lens mirror array 90. The lens mirror array 90 is positioned such that the optical axis in the sub-scanning direction of the incident-side lens surface 92 passes through the center in the sub-scanning direction of the aperture 785.

[0042] The holder 78 holds the reflector 72 and the light guide 74 inside the two side walls 781 and above the partition wall 783 on both sides with the bulging portion 784 sandwiched therebetween along the sub-scanning direction. The reflector 72 and the light guide 74 are held by an existing holding structure (not shown). Details of the holding structure of the reflector 72 and the light guide 74 are omitted.

[0043] The reflector 72 is, for example, a long rectangular plate extending in the main scanning direction. The reflector 72 has a reflecting surface facing a light diffusing portion (not shown) of the light guide 74. The light diffusing portion of the light guide 74 has, for example, unevenness on its surface. Or, the light diffusing portion of the light guide 74 has white ink applied to its surface. The reflector 72 has, for example, white ink applied to its reflecting surface. Or, the reflector 72 has a white resin formed in a rectangular plate shape on its reflecting surface. The reflector 72 has a function of reflecting the light leaking from the light diffusing portion of the light guide 74 back to the light guide 74.

[0044] The light guide 74 is, for example, a substantially columnar transparent resin long in the main scanning direction, and has the above-described light diffusing portion along the longitudinal direction on a part of its surface. The light guide 74 guides the light emitted from an LED light source (not shown) arranged at one end in its longitudinal direction. The reflector 72 reflects the light leaking from the light diffusing portion of the light guide 74 and returns it to the light guide 74.

[0045] Since there is the bulging portion 784 of the partition wall 783 of the holder 78 between the two light guides 74, it is necessary to arrange them at a certain distance apart from each other in the sub-scanning direction so that the bulging portion 784 does not create a shadow of the illumination light. On the other hand, if the two light guides 74 are separated in the sub-scanning direction, the angle of the illumination light hitting the image reading area on the original surface becomes large, and the change in illuminance becomes large when the distance between the original glass 82 and the original surface changes. For this reason, it is desirable to arrange the two light guides 74 as close to each other as possible in the sub-scanning direction.

[0046] The holder 78 has a plurality of bosses 786 protruding downward from the illustrated lower surface of the partition wall 783. The bosses 786 are provided, for example, at three locations: both ends and the center in the main scanning direction of the partition wall 783, on both sides in the sub-scanning direction of the bulging portion 784. These six bosses 786 are each for fixing the substrate 75 to the holder 78 using screws 787. Note that the holder 78 includes a plurality of bosses 788 for positioning the substrate 75 on the holder 78.

[0047] (Lens mirror array) Next, with reference to FIGS. 4 to 6, the details of the lens mirror array 90 incorporated in the reading module 70 will be described. FIG. 4 is a view of the lens mirror array 90 incorporated in the reading module 70 as seen from the main scanning direction. FIG. 5 is a perspective view of the lens mirror array 90 as seen from the side of the downstream mirror. FIG. 6 is a perspective view of the lens mirror array 90 as seen from the side of the emission-side lens.

[0048] As shown in FIGS. 4 to 6, the lens mirror array 90 has an elongated structure extending in its longitudinal direction (only a part is shown in FIGS. 5 and 6). The lens mirror array 90 has a plurality of transparent optical elements 91 arranged integrally in its longitudinal direction.

[0049] Here, the longitudinal direction of the lens mirror array 90 coincides with the main scanning direction (X direction) when incorporated in the reading module 70. Hereinafter, the lens mirror array 90, as being incorporated in the reading module 70, will also refer to its longitudinal direction as the main scanning direction or the X direction.

[0050] The plurality of optical elements 91 have the same shape. The shape of each optical element 91 is symmetric with respect to an imaginary central plane passing through the center in the longitudinal direction of the optical element 91 and orthogonal to the longitudinal direction.

[0051] The lens mirror array 90 has, in addition to a plurality of optical elements 91, extension portions 97 (only one is shown in FIG. 6) at both longitudinal ends thereof for an operator to grip the lens mirror array 90. When the operator holds the lens mirror array 90 by hand, it is desirable to have this extension portion 97 so as not to touch the surface that guides the reflected light from the original document.

[0052] For example, the lens mirror array 90 can be formed by integrally molding a transparent resin using a mold. The lens mirror array 90 can also be formed from transparent glass.

[0053] Each optical element 91 of the lens mirror array 90 guides diffused light from an object point to form an image at an image forming point on the image plane. One optical element 91 forms an image of light from a plurality of object points arranged in the main scanning direction on the image plane. For example, one optical element 91 forms an image of light from object points arranged within a width that is two to five times the pitch of the optical element 91 in the main scanning direction on the image plane. Each optical element 91 of the lens mirror array 90 reflects the incident light twice and then emits it, forming an erect image of the object point on the image plane.

[0054] Each optical element 91 of the lens mirror array 90 has, on its surface, an incident-side lens surface 92, an upstream-side mirror surface 93, a downstream-side mirror surface 94, and an exit-side lens surface 95. The incident-side lens surface 92, the downstream-side mirror surface 94, and the exit-side lens surface 95 are all free-form surfaces that are convex outward. The upstream-side mirror surface 93 is a flat surface. The other surfaces of the plurality of optical elements 91 each constitute one flat surface that extends in the main scanning direction over the entire length of the lens mirror array 90.

[0055] The incident-side lens surface 92 of the optical element 91 faces the aperture opening 785 in the bulging portion 784 of the holder 78. In other words, the lens mirror array 90 is fixed to the bulging portion 784 in the state shown in FIG. 3 where the incident-side lens surfaces 92 of the plurality of optical elements 91 face the aperture opening 785. The incident-side lens surface 92 has a positive optical power for making the light reflected by the original surface pass through the aperture opening 785 and then refracting and converging this incident light. That is, the incident-side lens surface 92 transmits and converges the incident light.

[0056] The upstream-side mirror surface 93 is adjacent to the incident-side lens surface 92 on the opposite side of the protruding portion 901. That is, the upstream-side mirror surface 93 is located on the optical path of the incident light incident through the incident-side lens surface 92. The upstream-side mirror surface 93 totally reflects or Fresnel-reflects the incident light incident through the incident-side lens surface 92 toward the downstream-side mirror surface 94.

[0057] Each optical element 91 has a protrusion 931 with a part protruding outward. The protrusion 931 has the upstream-side mirror surface 93 at its top. The plurality of protrusions 931 of the plurality of optical elements 91 are spaced apart from each other in the longitudinal direction. Each protrusion 931 has a light-shielding film 932 on its side surface. The light-shielding film 932 of each protrusion 931 prevents light from traveling through the side surface of each protrusion 931.

[0058] The downstream mirror surface 94 is continuous with respect to the incident-side lens surface 92 on the side opposite to the protruding portion 902. That is, the downstream mirror surface 94 is located on the optical path of the reflected light reflected by the upstream mirror surface 93. The downstream mirror surface 94 totally reflects or Fresnel-reflects the reflected light reflected by the upstream mirror surface 93 toward the exit-side lens surface 95. The downstream mirror surface 94 is a free-form surface having a positive optical power that reflects and converges light. For example, the downstream mirror surface 94 has a positive optical power in the sub-scanning direction. That is, the downstream mirror surface 94 converges the reflected light reflected by the upstream mirror surface 93 in the sub-scanning direction and totally reflects or Fresnel-reflects it toward the exit-side lens surface 95. The width of the downstream mirror surface 94 in the main scanning direction is narrower than the width of the optical element 91.

[0059] The exit-side lens surface 95 is continuous with respect to the downstream mirror surface 94 on the side opposite to the protruding portion 903. That is, the exit-side lens surface 95 is located on the optical path of the reflected light reflected by the downstream mirror surface 94. The exit-side lens surface 95 is a free-form surface having a positive optical power that transmits and converges the reflected light reflected by the downstream mirror surface 94. That is, the exit-side lens surface 95 transmits the reflected light reflected by the downstream mirror surface 94 and converges it onto the image sensor 76. The lens mirror array 90 has a light-blocking portion 96 that blocks the progress of light between the two downstream mirror surfaces 94 of two adjacent optical elements 91 in the main scanning direction. For example, the light-blocking portion 96 blocks the incident light. Therefore, the light-blocking portion 96 has a light-shielding film. Instead of blocking the light, the light-blocking portion 96 may direct the light traveling toward the image sensor 76 in another direction.

[0060] (Optical system of the reading module) Next, with reference to FIGS. 7 to 10, a configuration example of the optical system of the reading module having the lens mirror array according to the embodiment and a configuration example of the optical system of the reading module having the lens mirror array according to the conventional example will be described. FIG. 7 is a diagram schematically showing a first configuration example of the optical system of the reading module 70 having the lens mirror array 90 according to the embodiment. FIG. 8 is a diagram schematically showing a second configuration example of the optical system of the reading module 70 having the lens mirror array 90 according to the embodiment. FIG. 9 is a diagram schematically showing a third configuration example of the optical system of the reading module 70 having the lens mirror array 90 according to the embodiment. FIG. 10 is a diagram schematically showing a configuration example of the optical system of the reading module 70 having the lens mirror array 90 according to the conventional example.

[0061] As shown in FIG. 7, in the first configuration example of the optical system of the reading module 70 having the lens mirror array 90 according to the embodiment, the incident light on the incident-side lens surface 92 becomes convergent light by passing through the incident-side lens surface 92 and is reflected by the upstream-side mirror surface 93. The reflected light by the upstream-side mirror surface 93 is, with respect to the main scanning direction, subsequently reflected by the downstream-side mirror surface 94 and then once converges at the convergence point Pcm, and then becomes divergent light and enters the exit-side lens surface 95. Also, the reflected light by the upstream-side mirror surface 93 is, with respect to the sub-scanning direction, subsequently reflected by the downstream-side mirror surface 94 and then once converges at the convergence point Pcs, and then becomes divergent light and enters the exit-side lens surface 95. The incident light on the exit-side lens surface 95 becomes convergent light by passing through the exit-side lens surface 95 and forms an erect and same-magnification image on the image plane.

[0062] That is, in the first configuration example of the optical system of the reading module 70 having the lens mirror array 90 according to the embodiment, the incident-side lens surface 92 of the lens mirror array 90 converges the incident light once in the main scanning direction and the sub-scanning direction between the downstream-side mirror surface 94 and the exit-side lens surface 95. Also, the exit-side lens surface 95 converges the incident light and forms an erect and same-magnification image on the image plane.

[0063] As shown in FIG. 8, in the second configuration example of the optical system of the reading module 70 having the lens mirror array 90 according to the embodiment, the incident light on the incident-side lens surface 92 becomes convergent light by passing through the incident-side lens surface 92 and is reflected by the upstream-side mirror surface 93. The reflected light by the upstream-side mirror surface 93 is subsequently reflected by the downstream-side mirror surface 94 in the main scanning direction, then converges once at the convergence point Pcm, and then becomes divergent light and enters the exit-side lens surface 95. Also, the reflected light by the upstream-side mirror surface 93 converges once at the convergence point Pcs in the sub-scanning direction, then becomes divergent light, and is subsequently reflected by the downstream-side mirror surface 94 and enters the exit-side lens surface 95. The incident light on the exit-side lens surface 95 becomes convergent light by passing through the exit-side lens surface 95 and forms an erect and same-magnification image on the image plane.

[0064] That is, in the second configuration example of the optical system of the reading module 70 having the lens mirror array 90 according to the embodiment, the incident-side lens surface 92 of the lens mirror array 90 converges the incident light once in the main scanning direction between the downstream-side mirror surface 94 and the exit-side lens surface 95, and also converges the incident light once in the sub-scanning direction between the upstream-side mirror surface 93 and the downstream-side mirror surface 94. Also, the exit-side lens surface 95 converges the incident light and forms an erect and same-magnification image on the image plane.

[0065] As shown in FIG. 9, in the third configuration example of the optical system of the reading module 70 having the lens mirror array 90 according to the embodiment, the incident light on the incident-side lens surface 92 becomes convergent light by passing through the incident-side lens surface 92 and is reflected by the upstream-side mirror surface 93. The reflected light by the upstream-side mirror surface 93 is subsequently reflected by the downstream-side mirror surface 94 in the main scanning direction, then converges once at the convergence point Pcm, and then becomes divergent light and enters the exit-side lens surface 95. Further, the reflected light by the upstream-side mirror surface 93 converges once at the convergence point Pcs on the downstream-side mirror surface 94 in the sub-scanning direction and is reflected by the downstream-side mirror surface 94, then becomes divergent light, and then enters the exit-side lens surface 95. The incident light on the exit-side lens surface 95 becomes convergent light by passing through the exit-side lens surface 95 and forms an erect and same-magnification image on the image plane.

[0066] That is, in the second configuration example of the optical system of the reading module 70 having the lens mirror array 90 according to the embodiment, the incident-side lens surface 92 of the lens mirror array 90 converges the incident light once in the main scanning direction between the downstream-side mirror surface 94 and the exit-side lens surface 95, and converges the incident light once in the sub-scanning direction on the downstream-side mirror surface 94. Further, the exit-side lens surface 95 converges the incident light and forms an erect and same-magnification image on the image plane.

[0067] As shown in FIG. 10, in the configuration example of the optical system of the reading module 70 having the lens mirror array 90 according to the conventional example, the incident light on the incident-side lens surface 92 becomes convergent light by passing through the incident-side lens surface 92 and is reflected by the upstream-side mirror surface 93. The reflected light by the upstream-side mirror surface 93 converges once at the convergence point Pcm in the main scanning direction, and then is reflected by the downstream-side mirror surface 94 to become divergent light and enters the exit-side lens surface 95. Further, the reflected light by the upstream-side mirror surface 93 converges once at the convergence point Pcs in the sub-scanning direction, and then is reflected by the downstream-side mirror surface 94 to become divergent light and enters the exit-side lens surface 95. The incident light on the exit-side lens surface 95 becomes convergent light by passing through the exit-side lens surface 95 and forms an erect same-magnification image on the image plane.

[0068] That is, in the configuration example of the optical system of the reading module 70 having the lens mirror array 90 according to the conventional example, the incident-side lens surface 92 of the lens mirror array 90 converges the incident light once in the main scanning direction and the sub-scanning direction between the upstream-side mirror surface 93 and the downstream-side mirror surface 94. Further, the exit-side lens surface 95 converges the incident light and forms an erect same-magnification image on the image plane.

[0069] In the optical system of the reading module 70 having the lens mirror array 90 according to the embodiment, in any of the first to third configuration examples, the incident-side lens surface 92 of the lens mirror array 90 is common in that it converges the incident light once in the main scanning direction between the downstream-side mirror surface 94 and the exit-side lens surface 95. On the other hand, in the optical system of the reading module 70 having the lens mirror array 90 according to the conventional example, the incident-side lens surface 92 of the lens mirror array 90 converges the incident light once in the main scanning direction between the upstream-side mirror surface 93 and the downstream-side mirror surface 94, which is different from the optical system of the reading module 70 having the lens mirror array 90 according to the embodiment.

[0070] In the lens mirror array 90, in order to reduce stray light (to the OK level), it is important to prevent unnecessary light from reaching the adjacent downstream mirror surface 94. To this end, it is effective to shorten both the optical path length from the incident-side lens surface 92 to the upstream-side mirror surface 93 and the optical path length from the upstream-side mirror surface 93 to the downstream-side mirror surface 94.

[0071] In the optical system of the reading module 70 having the lens mirror array 90 according to the conventional example, in order to once converge light in the main scanning direction between the upstream-side mirror surface 93 and the downstream-side mirror surface 94, the optical path length from the incident-side lens surface 92 to the downstream-side mirror surface 94 is long, and stray light is likely to occur. In order to finally suppress the stray light, the lens pitch in the main scanning direction of the incident-side lens surface 92 is increased so that unnecessary light rays do not reach the adjacent downstream-side mirror surface 94. For this reason, the lens pitch of the incident-side lens surface 92 cannot be reduced, and sufficient depth-of-field performance cannot be achieved.

[0072] On the other hand, in the optical system of the reading module 70 having the lens mirror array 90 according to the embodiment, in order to once converge light in the main scanning direction between the downstream-side mirror surface 94 and the exit-side lens surface 95, the sum of the optical path length from the incident-side lens surface 92 to the upstream-side mirror surface 93 and the optical path length from the upstream-side mirror surface 93 to the downstream-side mirror surface 94 is shorter than that of the optical system of the reading module 70 having the lens mirror array 90 according to the conventional example, and stray light generated by light leaking to the adjacent downstream-side mirror surface 94 is less likely to occur. As a result, even if the lens pitch of the incident-side lens surface 92 is reduced, the stray light can be eliminated or reduced.

[0073] Table 1 shows the results of comparing the generation levels of stray light depending on where the light is once converged.

[0074]

Table 1

[0075] As can be seen from Table 1, there was no significant difference in the sub-scanning direction before and after the downstream mirror surface 94, but there was a significant difference in the main scanning direction before and after the downstream mirror surface 94. Specifically, less stray light was generated when the light was converged after passing through the downstream mirror surface 94, compared to when the light was converged in front of the downstream mirror surface 94 or on the downstream mirror surface 94, and it was at the OK level.

[0076] (Effect) In the optical system of the reading module 70 having the lens mirror array 90 according to the embodiment, the incident-side lens surface 92 of the lens mirror array 90 once converges the incident light in the main scanning direction between the downstream mirror surface 94 and the exit-side lens surface 95. Thereby, the generation of stray light can be reduced and suppressed. For this reason, the lens mirror array 90 according to the embodiment can obtain a wide depth of field performance.

[0077] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and its equivalent scope.

[0078] The invention disclosed in the embodiment is described below. [1] having a plurality of optical elements arranged in the main scanning direction, the optical element is an incident-side lens surface that transmits and converges incident light, an upstream mirror surface that reflects the light incident through the incident-side lens surface, a downstream mirror surface that reflects the light reflected by the upstream mirror surface, and an exit-side lens surface that transmits and converges the light reflected by the downstream mirror surface. The incident-side lens surface once converges the incident light in the main scanning direction between the downstream mirror surface and the exit-side lens surface. Lens mirror array. [2] The exit-side lens surface converges the light that once converges and then diverges again in the main scanning direction to form an erect and same-magnification image on the image plane. The lens mirror array according to [1]. [3] The optical element has a protrusion having the upstream mirror surface as its top, and the protrusion has a light-shielding film on its side surface that blocks the progress of light through the side surface. The lens mirror array according to [1]. [4] The incident-side lens surface once converges the incident light in the sub-scanning direction between the downstream mirror surface and the exit-side lens surface. The lens mirror array according to [1]. [5] The incident-side lens surface once converges the incident light in the sub-scanning direction between the upstream mirror surface and the downstream mirror surface. The lens mirror array according to [1]. [6] The incident-side lens surface once converges the incident light in the sub-scanning direction on the downstream mirror surface. The lens mirror array according to [1]. [7] The upstream mirror surface is flat. The lens mirror array according to [1]. [8] The downstream mirror surface is curved. The lens mirror array according to [1]. [9] The downstream mirror surface has positive optical power. The lens mirror array according to [8].

[10] Between the two downstream mirror surfaces of the two optical elements adjacent to the main scanning direction, there is a propagation blocking portion that blocks the propagation of light. The lens mirror array according to [1].

Explanation of symbols

[0079] 10… Printer, 11… Paper feed cassette, 12… Manual feed tray, 13… Paper feed roller, 141~144… Toner cartridge, 151~154… Image forming unit, 16… Optical scanning device, 17… Transfer belt, 171… Driving roller, 18… Secondary transfer roller, 19… Fixing unit, 191… Heating roller, 192… Pressing roller, 20… Scanner, 30… Operation panel, 31… Touch panel, 32… Input device, 41… Photoconductor drum, 42… Charging device, 43… Developing device, 44… Secondary transfer roller, 45… Cleaner, 46… Discharge lamp, 50… Duplex unit, 60… Output tray, 70… Reading module, 72… Reflector, 74… Light guide, 75… Substrate, 76… Image sensor, 78… Holder, 781… Side wall, 782… End wall, 783… Partition wall, 784… Bulging portion, 785… Aperture opening, 786… Boss, 787… Screw, 788… Boss, 80… Original document feeder, 81… Original document tray, 82… Original document glass, 90… Lens mirror array, 901… Protruding portion, 902… Protruding portion, 903… Protruding portion, 91… Optical element, 92… Incident side lens surface, 93… Upstream side mirror surface, 931… Protrusion, 932… Light shielding film, 94… Downstream side mirror surface, 95… Exit side lens surface, 96… Propagation blocking portion, 97… Extended portion, 97… Extension portion, 100… Image forming apparatus.

Claims

1. Having a plurality of optical elements arranged in the main scanning direction, The optical element is An incident-side lens surface that transmits and converges incident light, An upstream-side mirror surface that reflects light incident through the incident-side lens surface, A downstream-side mirror surface that reflects the light reflected by the upstream-side mirror surface, And an exit-side lens surface that transmits and converges the light reflected by the downstream-side mirror surface, The incident-side lens surface converges incident light once in the main scanning direction between the downstream-side mirror surface and the exit-side lens surface, A lens mirror array.

2. The exit-side lens surface converges light that diverges again after converging once in the main scanning direction and forms an erect and same-magnification image on the image plane, The lens mirror array according to Claim 1.

3. The optical element has a protrusion having the upstream-side mirror surface at its top, and the protrusion has a light-shielding film on its side surface that blocks light from traveling through the side surface, The lens mirror array according to Claim 1.

4. The incident-side lens surface converges incident light once in the sub-scanning direction between the downstream-side mirror surface and the exit-side lens surface, The lens mirror array according to Claim 1.

5. The incident-side lens surface converges incident light once in the sub-scanning direction between the upstream-side mirror surface and the downstream-side mirror surface, The lens mirror array according to Claim 1.

Images