JP2010286741A - Erecting unit magnification lens array plate, optical scanning unit and image reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an erecting unit magnification lens array plate that reduces flare noise, and an optical scanning unit using the erecting unit magnification lens array plate and an image reader. <P>SOLUTION: In the erecting unit magnification lens array plate 11, a first lens array plate 24 having a plurality of first lenses 24a and second lenses 24b, and a second lens array plate 26 having a plurality of third lenses 26a and fourth lenses 26b are layered. The erecting unit magnification lens array plate 11 includes a first light shielding wall 50 erected so as to surround the first lens 24a, a second light shielding wall 52 erected so as to surround the fourth lens, a first aperture 54 formed on the first lens 24a by the first light shielding wall 50, and a second aperture 56 formed on the fourth lens 26b by the second light shielding wall 52. At least one of the first aperture 54 and the second aperture 56 is formed so that an aperture diameter ID on a lens side may be larger than an aperture diameter OD on an opposite side. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an erecting equal-magnification lens array plate used in an image reading apparatus and an image forming apparatus, and an optical scanning unit and an image reading apparatus using the erecting equal-magnification lens array plate.

  2. Description of the Related Art Conventionally, an apparatus using an erecting equal magnification imaging optical system is known as an image reading apparatus such as a scanner. When an erecting equal-magnification imaging optical system is used, the apparatus can be made more compact than in the case of a reduction imaging optical system. In the case of an image reading apparatus, the erecting equal-magnification imaging optical system includes a line light source, an erecting equal-magnification lens array, and a line image sensor.

  As the erecting equal magnification lens array in the erecting equal magnification imaging optical system, a rod lens array capable of forming an erecting equal magnification image is used. In the rod lens array, rod lenses are usually arranged in the longitudinal direction of the lens array (main scanning direction of the image reading apparatus). Increasing the number of rows of rod lenses can improve the light transmission rate and reduce the amount of transmitted light, but in the case of a rod lens array, the number of rows of rod lenses is generally 1 to 2 depending on the price. Is.

  On the other hand, as an erecting equal-magnification lens array, an erecting structure in which a plurality of transparent flat lens array plates in which a plurality of minute convex lenses are regularly arranged on one side or both sides are laminated so that the optical axes of the individual convex lenses coincide with each other. A 1 × lens array plate can also be constructed. Since such an erecting equal-magnification lens array plate can be formed by a method such as injection molding, a plurality of rows of erecting equal-magnification lens arrays can be manufactured relatively inexpensively.

  In the erecting equal-magnification lens array plate, there is no wall for isolating the light beam between the adjacent lenses, so that the light beam obliquely incident on the erecting equal-magnification lens array plate proceeds obliquely through the plate and is adjacent to the convex lens. There is a problem of stray light that enters and exits and generates noise (also called ghost).

  In view of this, there is known one in which a light-shielding wall for removing stray light that does not contribute to image formation is formed on the surface of an erecting equal-magnification lens array plate (see, for example, Patent Document 1).

JP 2009-069801 A

  However, when a light shielding wall is provided on the surface of the erecting equal-magnification lens array plate, light reflected by the light shielding wall may become flare noise.

  The present invention has been made in view of such circumstances, and an object thereof is to provide an erecting equal-magnification lens array plate capable of reducing flare noise, an optical scanning unit using the erecting equal-magnification lens array plate, and an image. To provide a reader.

  In order to solve the above problems, an erecting equal-magnification lens array plate according to an aspect of the present invention includes a plurality of first lenses regularly arranged on a first surface and a second surface facing the first surface. A first lens array plate having a plurality of regularly arranged second lenses, a plurality of third lenses regularly arranged on the third surface, and a fourth surface facing the third surface regularly A second lens array plate having a plurality of fourth lenses disposed in the first lens array plate and the second lens array plate so that a pair of corresponding lenses forms a coaxial lens system. The second surface and the third surface are stacked so as to face each other, receive light from the line-shaped light source on the first surface side, and form an erect life-size image of the line-shaped light source on the image surface on the fourth surface side. This is an erecting equal-magnification lens array plate. A first light-shielding wall standing up to surround the first lens, a second light-shielding wall standing up to surround the fourth lens, and a first opening formed on the first lens by the first light-shielding wall And a second opening formed on the fourth lens by the second light shielding wall, and at least one of the first opening and the second opening has an opening diameter on the lens side that is larger than the opening diameter on the opposite side. Is also formed to be large.

  According to this aspect, since the light reaching the image plane after being reflected by the first light shielding wall or the fourth light shielding wall is reduced, flare noise can be reduced.

  At least one of the first opening and the second opening may be formed such that the lens-side opening diameter is larger than the lens diameter.

  At least one of the first opening and the second opening may be formed so that the opening diameter decreases in a tapered shape from the lens side toward the opposite side.

  At least one of the first surface and the fourth surface may be provided with a light shielding member so as to cover a region between adjacent lenses.

  In at least one of the first surface and the fourth surface, a surface roughening treatment may be applied to a region between adjacent lenses.

  Another aspect of the present invention is an optical scanning unit. The optical scanning unit transmits the line-shaped light source that irradiates light to the read image, the above-described erecting equal-magnification lens array plate that collects the light reflected from the read image, and the erecting equal-magnification lens array plate. A line image sensor that receives the received light.

  According to this aspect, since the optical scanning unit is configured using the above-described erecting equal-magnification lens array plate, the line image sensor can receive an erecting equal-magnification image with reduced flare noise.

  Yet another embodiment of the present invention is an image reading apparatus. This apparatus includes an optical scanning unit and an image processing unit that processes an image signal detected by the optical scanning unit.

  According to this aspect, since the image reading apparatus is configured using the above-described optical scanning unit, it is possible to generate high-quality image data from which flare noise is suitably removed.

  It should be noted that any combination of the above-described constituent elements and a representation of the present invention converted between a method, an apparatus, a system, etc. are also effective as an aspect of the present invention.

  According to the present invention, it is possible to provide an erecting equal-magnification lens array plate capable of reducing flare noise, and an optical scanning unit and an image reading apparatus using the erecting equal-magnification lens array plate.

It is a figure for demonstrating the image reading apparatus which concerns on embodiment of this invention. It is sectional drawing in the main scanning direction of a part of optical scanning unit. FIG. 6 is a plan view of a part of an erecting equal-magnification lens array plate as viewed from the document side. It is a figure for demonstrating operation | movement of the erecting equal-magnification lens array plate which concerns on a comparative example. It is a figure for demonstrating operation | movement of the erecting equal-magnification lens array plate which concerns on embodiment of this invention. It is a figure for demonstrating the erecting equal-magnification lens array plate which concerns on another embodiment of this invention. It is a figure for demonstrating the erecting equal-magnification lens array plate which concerns on another embodiment of this invention. It is a figure for demonstrating the erecting equal-magnification lens array plate which concerns on another embodiment of this invention. It is a figure for demonstrating the erecting equal-magnification lens array plate which concerns on another embodiment of this invention. It is a figure which shows the change of the noise ratio at the time of changing opening diameter ID.

  FIG. 1 is a diagram for explaining an image reading apparatus 100 according to an embodiment of the present invention. As shown in FIG. 1, the image reading apparatus 100 includes a housing 102, a glass plate 14 as a document table on which the document G is placed, an optical scanning unit 10 accommodated in the housing 102, and an optical scanning unit. 10 includes a driving mechanism (not shown) that scans 10, an image processing unit (not shown) that processes data read by the optical scanning unit 10, and the like.

  The optical scanning unit 10 includes a linear light source 16 that irradiates light on a document G placed on a glass plate 14, an erecting equal-magnification lens array plate 11 that collects reflected light from the document G, and erecting A line image sensor (photoelectric conversion element) 20 that receives the light condensed by the equal-magnification lens array plate 11, and a housing (see FIG. Not shown).

  The line light source 16 is a light source that emits substantially linear light. The line light source 16 is fixed so that the optical axis of the irradiation light passes through the intersection of the optical axis Ax of the erecting equal-magnification lens array plate 11 and the upper surface of the glass plate 14. The light emitted from the line light source 16 is applied to the original G placed on the glass plate 14. The light irradiated on the original G is reflected by the original G toward the erecting equal-magnification lens array plate 11.

  As will be described later, the erecting equal-magnification lens array plate 11 forms a coaxial lens system in which a pair of lenses corresponding to the first lens array plate 24 and the second lens array plate 26 each having a plurality of convex lenses formed on both surfaces thereof. It is laminated so as to. The first lens array plate 24 and the second lens array plate 26 are held in a stacked state by a holder (not shown). The erecting equal-magnification lens array plate 11 is mounted on the image reading apparatus 100 so that the longitudinal direction thereof coincides with the main scanning direction and the short side direction thereof coincides with the sub scanning direction.

  The erecting equal-magnification lens array plate 11 receives line-shaped light reflected from the document G located above, and forms an erecting equal-magnification image on the image surface located below, that is, the light receiving surface of the line image sensor 20. Form. The image reading apparatus 100 can read the document G by scanning the optical scanning unit 10 in the sub-scanning direction.

  Next, the erecting equal-magnification lens array plate 11 according to the embodiment of the present invention will be described with reference to FIGS. FIG. 2 is a cross-sectional view of a part of the optical scanning unit 10 in the main scanning direction. In FIG. 2, the vertical direction is the main scanning direction (longitudinal direction) of the erecting equal-magnification lens array plate 11, and the depth direction is the sub-scanning direction (short direction). FIG. 3 is a plan view of a part of the erecting equal-magnification lens array plate 11 as viewed from the original G side. In FIG. 3, the horizontal direction is the main scanning direction (longitudinal direction) of the erecting equal-magnification lens array plate 11, and the vertical direction is the sub-scanning direction (short direction).

  As described above, the erecting equal-magnification lens array plate 11 is configured by laminating the first lens array plate 24 and the second lens array plate 26. The first lens array plate 24 and the second lens array plate 26 are rectangular plates having a thickness t, and a plurality of convex lenses are arrayed on both surfaces thereof.

  The first lens array plate 24 and the second lens array plate 26 are formed by injection molding. The material of the first lens array plate 24 and the second lens array plate 26 is preferably one that can be used for injection molding, has high light transmittance with respect to light in a necessary wavelength band, and low water absorption. Examples of desirable materials include cycloolefin resins, olefin resins, norbornene resins, and polycarbonates.

  On the first surface 24c, which is one surface of the first lens array plate 24, a plurality of first lenses 24a are arranged in a line along the longitudinal direction of the first lens array plate 24 at a predetermined lens pitch P. Has been. The lens diameter D of the first lens 24a is smaller than the lens pitch P. Accordingly, a first flat portion 24e, which is a region where no lens is formed, is formed between adjacent first lenses 24a. On the second surface 24 d facing the first surface 24 c of the first lens array plate 24, a plurality of second lenses 24 b having a lens diameter D are arranged in a line along the longitudinal direction of the first lens array plate 24. The second flat portion 24f is provided between the adjacent second lenses 24b. In the present embodiment, the lens diameter D is a diameter of a region that effectively functions as a lens. That is, the diameter of the portion of the lens that is not covered with the light shielding member.

  On the third surface 26 c, which is one surface of the second lens array plate 26, a plurality of third lenses 26 a having a lens diameter D are arranged in a line along the longitudinal direction of the second lens array plate 26, with a lens pitch P. The third flat portion 26e is provided between the adjacent third lenses 26a. On the fourth surface 26d facing the third surface 26c, a plurality of fourth lenses 26b having a lens diameter D are arranged in a line along the longitudinal direction of the second lens array plate 26 at a lens pitch P. A fourth flat portion 26f is formed between the adjacent fourth lenses 26b.

  In the present embodiment, the shape of the first lens 24a, the second lens 24b, the third lens 26a, and the fourth lens 26b is spherical, but it may be an aspherical surface.

  In the present embodiment, the first light shielding member 40 is provided on the first surface 24 c of the first lens array plate 24. The first light shielding member 40 is provided so as to cover the region of the first surface 24c other than the effective region of the first lens 24a, and the light transmission of the first flat portion 24e is blocked by the first light shielding member 40. Is done. Here, the effective area of the lens is a portion having a function as a lens.

  Similarly, a second light shielding member 42, a third light shielding member 44, and a fourth light shielding member 46 are provided on the second surface 24d, the third surface 26c, and the fourth surface 26d, respectively. The light blocking member 42, the third light blocking member 44, and the fourth light blocking member 46 block light transmission through the second flat portion 24f, the third flat portion 26e, and the fourth flat portion 26f.

  The first light shielding member 40, the second light shielding member 42, the third light shielding member 44, and the fourth light shielding member 46 have black ink or the like on the first surface 24c, the second surface 24d, the third surface 26c, and the fourth surface 26d. It can be formed by printing a light shielding pattern using the light absorbing material. The first light shielding member 40, the second light shielding member 42, the third light shielding member 44, and the fourth light shielding member 46 are directly formed on the first surface 24c, the second surface 24d, the third surface 26c, and the fourth surface 26d. Instead, the first surface 24c, the second surface 24d, the third surface 26c, and the fourth surface 26d may be spaced apart from each other. Further, the second light shielding member 42 and the third light shielding member 44 may be combined to form one light shielding member. In this case, the imaged light blocking member can be disposed between the first lens array plate 24 and the second lens array plate 26.

  Further, in the present embodiment, the first light shielding wall 50 is erected on the first light shielding member 40 of the first surface 24c so as to surround the periphery of each first lens 24a. A first opening 54 is formed on each first lens 24 a by the first light shielding wall 50. The first light shielding wall 50 has a function of blocking stray light from entering the first lens 24a. The height of the first light shielding wall 50 is set to a height at which light rays up to a predetermined maximum viewing angle can be removed. In FIG. 2, the first light shielding wall 50 and the first light shielding member 40 are in contact with each other, but there may be a gap between the first light shielding wall 50 and the first light shielding member 40.

  As shown in FIG. 3, the first opening 54 is a circular opening in plan view, and is arranged so that the center thereof is located on the optical axis of the first lens 24a. Further, as shown in FIG. 2, the first opening 54 is formed so that the opening diameter decreases in a tapered shape from the first lens 24a side to the opposite side (the document G side). Accordingly, the first opening 54 is formed such that the opening diameter ID on the first lens 24a side is larger than the opening diameter OD on the document G side.

  The first opening 54 is formed such that the opening diameter ID on the first lens 24a side is larger than the lens diameter D of the first lens 24a. Therefore, a region 40a of the first light shielding member 40 (hereinafter referred to as a first light shielding member exposed region 40a) that is not covered by the first light shielding wall 50 is formed around the first lens 24a. 2 and 3, the lens diameter D of the first lens 24a is shown larger than the opening diameter OD, but the relationship between the lens diameter D and the opening diameter OD is not limited to this, and for example, the lens diameter is It may be smaller than the opening diameter OD.

  Similarly, the second light shielding wall 52 is erected on the fourth light shielding member 46 on the fourth surface 26d so as to surround the periphery of each fourth lens 26b. The second light shielding wall 52 forms a second opening 56 on each fourth lens 26b. The second light shielding wall 52 has a function of removing stray light emitted from the fourth lens 26b. The height of the second light shielding wall 52 is set to be the same as that of the first light shielding wall 50. In FIG. 2, the second light shielding wall 52 and the fourth light shielding member 46 are in contact with each other, but there may be a gap between the second light shielding wall 52 and the fourth light shielding member 46.

  As shown in FIG. 2, the second opening 56 is formed such that the opening diameter decreases in a tapered shape from the fourth lens 26b side toward the opposite side (line image sensor 20 side). Accordingly, the second opening 56 is formed such that the opening diameter on the fourth lens 26b side is larger than the opening diameter on the line image sensor 20 side.

  The second opening 56 is formed such that the opening diameter on the fourth lens 26b side is larger than the lens diameter D of the fourth lens 26b. Therefore, a region 46a of the fourth light shielding member 46 (hereinafter referred to as a fourth light shielding member exposed region 46a) that is not covered by the second light shielding wall 52 is formed around the fourth lens 26b.

  The first light shielding wall 50 and the second light shielding wall 52 can be formed by a method such as injection molding using a light absorbing material such as black ABS resin. The first light shielding wall 50 and the second light shielding wall 52 may be formed by laminating a black resin paint on the first surface 24c and the fourth surface 26d.

  The first lens array plate 24 and the second lens array plate 26 thus formed with the lens, the light shielding member, and the light shielding wall have the corresponding first lens 24a, second lens 24b, third lens 26a, and fourth lens 26b. The second surface 24d and the third surface 26c are laminated so as to form a coaxial lens system. In the present embodiment, the second lens 24b on the second surface 24d and the third lens 26a on the third surface 26c are in contact with each other, but the second lens 24b and the third lens 26a may be separated from each other. Good.

  In the erecting equal-magnification lens array plate 11 configured as described above, the distance from the first lens 24a to the document G and the distance from the fourth lens 26b to the line image sensor 20 are the predetermined working distance WD. Incorporated into the image reading apparatus 100.

  Next, the operation of the erecting equal-magnification lens array plate 11 according to the present embodiment will be described. Before describing the operation of the erecting equal-magnification lens array plate 11, a comparative example is first shown. FIG. 4 is a diagram for explaining the operation of the erecting equal-magnification lens array plate 211 according to the comparative example. In the erecting equal-magnification lens array plate 211 according to the comparative example, the first light shielding wall 50 and the second light shielding wall 52 are formed so that the shapes of the first opening 54 and the second opening 56 are cylindrical. Yes.

  First, consider the light L1 (broken line) emitted from the point 60 on the document G located on the optical axis of the first lens 24a. Usually, the light L <b> 1 that attempts to enter the first lens array plate 24 at an incident angle θ <b> 1 larger than the imaging light is absorbed by the first light shielding wall 50. However, the light L1 is not completely absorbed by the first light shielding wall 50 even when a light absorbing material is used, and a part of the light L1 is incident on the first lens 24a due to Fresnel reflection. The light L1 reflected by the first light shielding wall 50 enters the line image sensor 20 after passing through the first lens 24a, the second lens 24b, the third lens 26a, and the fourth lens 26b as shown in FIG. So-called flare noise occurs.

  Next, the light L2 (solid line) emitted from the point 62 on the original G that is off the optical axis of the first lens 24a will be considered. In this case, part of the light L 2 that is about to enter the first lens array plate 24 at an incident angle θ 2 that is larger than the incident angle θ 1 is reflected by Fresnel at the first light shielding wall 50. As shown in FIG. 4, the light L2 passes through the first lens 24a, the second lens 24b, the third lens 26a, and the fourth lens 26b, and then enters the line image sensor 20, resulting in so-called flare noise. .

  Although the flare noise generated by the reflection on the first light shielding wall 50 has been described with reference to FIG. 4, the flare noise is also generated by the reflection on the second light shielding wall 52.

  FIG. 5 is a diagram for explaining the operation of the erecting equal-magnification lens array plate 11 according to the embodiment of the present invention. First, as in the comparative example of FIG. 4, the light L1 (from the point 60 on the original G located on the optical axis of the first lens 24a and entering the first lens array plate 24 at the incident angle θ1 ( Consider the broken line. In the present embodiment, since the first opening 54 is formed so that the opening diameter ID on the first lens 24a side is larger than the opening diameter OD on the document G side, the light L1 is emitted from the first light shielding wall 50. Without being collided with the light, it directly enters the first light shielding member exposed region 40a and is absorbed. Therefore, flare noise attributed to the light L1 does not occur.

  Next, consider the light L2 (solid line) emitted from the point 62 on the original G that is off the optical axis of the first lens 24a and entering the first lens array plate 24 at the incident angle θ2. The light L2 is reflected by the first light shielding wall 50. In the present embodiment, since the first opening 54 is formed so that the opening diameter decreases in a tapered shape from the first lens 24a side to the opposite side (document G side), the first of the reflected light L2 is formed. The incident angle with respect to the lens array plate 24 is smaller than that in the case of FIG. Therefore, the light L2 reflected by the first light shielding wall 50 enters the first light shielding member exposed region 40a, not the first lens 24a, and is absorbed. Therefore, flare noise attributed to the light L2 does not occur.

  Although the flare noise reducing action attributed to the reflection at the first light shielding wall 50 has been described with reference to FIG. 5, the reflection at the second light shielding wall 52 is achieved by forming the second light shielding wall 52 as described above. The flare noise attributed to is also reduced.

  As described above, the erecting equal-magnification lens array plate 11 can reduce flare noise caused by reflection on the first light shielding wall 50 and the second light shielding wall 52. Further, the erecting equal-magnification lens array plate 11 can remove the stray light that is incident on the erecting equal-magnification lens array plate 11 at an angle and causes ghost by the first light shielding wall 50 or the second light shielding wall 52. it can. Therefore, the erecting equal-magnification lens array plate 11 according to the present embodiment can form a good-quality erecting equal-magnification image with reduced noise.

  In the erecting equal-magnification lens array plate 11 shown in FIG. 2, both the first opening 54 and the second opening 56 are formed so that the opening diameter on the lens side is larger than the opening diameter on the opposite side. However, if at least one of the first opening 54 and the second opening 56 is formed so that the opening diameter on the lens side is larger than the opening diameter on the opposite side, it is effective in reducing flare noise.

  FIG. 6 is a view for explaining an erecting equal-magnification lens array plate 611 according to another embodiment of the present invention. The erecting equal-magnification lens array plate 611 according to the present embodiment does not include the first light shielding member and the fourth light shielding member, and the first light shielding wall 50 and the second light directly on the first surface 24c and the fourth surface 26d. The point which provides the light-shielding wall 52 is different from the erecting equal-magnification lens array plate 11 shown in FIG. Since the other configuration is the same as that of the erecting equal-magnification lens array plate 11 shown in FIG. 2, the same reference numerals are used for the corresponding components, and description thereof is omitted.

  The operation of the erecting equal-magnification lens array plate 611 formed in this way will be described. First, similarly to FIGS. 4 and 5, the light L1 (from the point 60 on the original G located on the optical axis of the first lens 24a and entering the first lens array plate 24 at the incident angle θ1 ( Consider the broken line. Also in the present embodiment, since the first opening 54 is formed so that the opening diameter on the first lens 24 a side is larger than the opening diameter on the document G side, the light L 1 collides with the first light shielding wall 50. do not do. However, in the present embodiment, since the first light shielding member is not provided on the first flat portion 24e, the light L1 enters the first lens array plate 24 from the first flat portion 24e. Thereafter, the light L1 enters the second light shielding member 42 and is absorbed.

  Next, consider the light L2 (solid line) emitted from the point 62 on the original G that is off the optical axis of the first lens 24a and entering the first lens array plate 24 at the incident angle θ2. The light L2 is reflected by the first light shielding wall 50. Also in the present embodiment, since the first opening 54 is formed so that the opening diameter decreases in a tapered shape from the first lens 24a side toward the document G side, the first lens array plate of the reflected light L2 is formed. The incident angle with respect to 24 is smaller than in the case of FIG. However, in the present embodiment, since the first light shielding member is not provided on the first flat portion 24e, the light L2 enters the first lens array plate 24 from the first flat portion 24e. Thereafter, the light L1 enters the second light shielding member 42 and is absorbed.

  As described above, the erecting equal-magnification lens array plate 611 according to the present embodiment can also reduce flare noise caused by reflection on the first light shielding wall 50 and the second light shielding wall 52. The erecting equal-magnification lens array plate 611 has an advantage that the manufacturing process can be reduced because the first light shielding member and the fourth light shielding member are not provided on the first surface 24c and the fourth surface 26d.

  FIG. 7 is a view for explaining an erecting equal-magnification lens array plate 711 according to still another embodiment of the present invention. Similar to the erecting equal-magnification lens array plate 611 shown in FIG. 6, the erecting equal-magnification lens array plate 711 according to the present embodiment has a first light shielding member and a fourth light-shielding member on the first surface 24c and the fourth surface 26d. A light shielding member is not provided. Further, in the erecting equal-magnification lens array plate 711, the first flat portion 24e of the first surface 24c and the fourth flat portion 26f of the fourth surface 26d are roughened. Since the other configuration is the same as that of the erecting equal-magnification lens array plate 11 shown in FIG. 2, the same reference numerals are used for the corresponding components, and description thereof is omitted. The roughening treatment may be performed by forming a roughened portion on an injection mold for forming the lens array plate. Or you may perform a roughening process by performing a blast process and an etching process after injection molding.

  The operation of the erecting equal-magnification lens array plate 711 formed in this way will be described. Here, the light L3 (broken line) emitted from the point 70 on the original G and incident on the first flat portion 24e of the first surface 24c with a large incident angle will be considered. As shown in FIG. 7, the light L3 enters the line image sensor 20 through the second lens 24b, the third lens 26a, and the fourth lens 26b, and ghost noise is generated. When the first flat portion 24e is not roughened, most of the light L3 incident on the first flat portion 24e contributes to the generation of ghost noise.

  However, in the erecting equal-magnification lens array plate 711 according to the present embodiment, the first flat portion 24e is subjected to a roughening process, so that the light L3 is roughened as indicated by an arrow 72 in FIG. Scattered by the converted first flat portion 24e. Accordingly, since the amount of the light L3 reaching the line image sensor 20 is reduced, ghost noise can be reduced. The effect of reducing flare noise is the same as that of the erecting equal-magnification lens array plate 11 shown in FIG.

  In the erecting equal-magnification lens array plate 711 shown in FIG. 7, both the first flat portion 24e and the fourth flat portion 26f are roughened, but if at least one of them is roughened Effective in reducing ghost noise.

  FIG. 8 is a view for explaining an erecting equal-magnification lens array plate 811 according to still another embodiment of the present invention. FIG. 8 is an enlarged view of one first lens 24a and the surrounding area. As shown in FIG. 8, the erecting equal-magnification lens array plate 811 according to the present embodiment is different from the erecting equal-magnification lens array plate 11 shown in FIG.

  Also in the present embodiment, the first opening 54 is formed such that the opening diameter ID on the first lens 24a side is larger than the opening diameter OD on the opposite side. The first opening 54 is formed so that the opening diameter ID on the first lens 24a side is larger than the lens diameter D of the first lens 24a. Here, in the present embodiment, the first opening 54 is constant (ID) from the first lens 24a side to the document side end, and the opening diameter is only at the document side end. It is formed so as to be smaller than ID. Even when the first opening 54 is formed in such a shape, flare noise can be reduced because the reflected light from the first light shielding wall 50 is absorbed by the first light shielding member exposed region 40a.

  FIG. 9 is a view for explaining an erecting equal-magnification lens array plate 911 according to still another embodiment of the present invention. FIG. 9 is an enlarged view of one first lens 24a and the surrounding area. As shown in FIG. 9, the erecting equal-magnification lens array plate 911 according to the present embodiment is different from the erecting equal-magnification lens array plate 11 shown in FIG.

  Also in the present embodiment, the first opening 54 is formed such that the opening diameter ID on the first lens 24a side is larger than the opening diameter OD on the opposite side. The first opening 54 is formed so that the opening diameter ID on the first lens 24a side is larger than the lens diameter D of the first lens 24a. Here, in the present embodiment, the first opening 54 is formed such that the opening diameter decreases in a curved manner from the first lens 24a side toward the document side. Even when the first opening 54 is formed in such a shape, flare noise can be reduced because the reflected light from the first light shielding wall 50 is absorbed by the first light shielding member exposed region 40a.

  FIG. 10 is a diagram illustrating a change in the noise ratio when the opening diameter ID is changed. Here, in the ray tracing simulation, a point-like ray is emitted under the condition of 90 degrees Lambertian over the region in the main scanning direction of the erecting equal-magnification lens array plate, and the imaged light that has reached a specific point on the image plane The light amount was defined as the imaging light transmission light amount, and the light amount reaching other than a specific point was defined as the noise transmission light amount. This was carried out in a line extending in the main scanning direction. The value obtained by dividing the total noise transmission light amount by the imaging light transmission light amount was taken as the noise ratio.

  The conditions for the simulation were as follows: the lens arrangement is a single line arrangement, the lens working distance WD = 3.3 mm, the thickness t = 1.6 mm of the first lens array plate and the second lens array plate, the lens pitch = 0.65 mm, and the lens The diameter = 0.5 mm, the refractive index n = 1.53, the height of the first light shielding wall and the second light shielding wall = 0.7 mm, and the opening diameter OD = 0.5 mm. Under these conditions, the aperture ratio ID was changed to 0.6 mm, 0.63 mm, and 0.65 mm with and without the light shielding member, respectively, and the noise ratio was calculated. Further, as a comparative example, a simulation was performed when the opening diameter ID was equal to the opening diameter OD (ID = OD = 0.5 mm), and how much the noise ratio was reduced from this comparative example was shown. Specifically, the simulation in the case of “with light shielding member” in FIG. 10 uses the erecting equal-magnification lens array plate 11 shown in FIG. 2 as a model, and the simulation in the case of “without light shielding member” in FIG. The erecting equal-magnification lens array plate 611 shown is used as a model. Further, the “comparative example” simulation of FIG. 10 uses the erecting equal-magnification lens array plate 211 shown in FIG. 4 as a model.

  As shown in FIG. 10, in the comparative example in which the opening diameter ID is 0.5 mm, the noise ratio is 47%. On the other hand, when the opening diameter ID is larger than the opening diameter OD, the noise ratio is smaller than that of the comparative example regardless of the presence or absence of the light shielding member. In particular, when there is a light shielding member and the aperture diameter ID = 0.65 mm, the noise ratio is 11%, which is reduced to 23% of the comparative example. This simulation shows that the erecting equal-magnification lens array plate according to the present embodiment is effective in reducing noise.

  The present invention has been described based on the embodiments. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to combinations of the respective constituent elements and processing processes, and such modifications are also within the scope of the present invention. is there.

  In the above-described embodiment, the lenses on each lens surface are arranged in a line in the main scanning direction, but the arrangement pattern of the lenses is not limited to this. For example, when the lenses are arranged in two lines in the main scanning direction, The present invention can be applied even when arranged in a square arrangement.

  In the above-described embodiment, the light shielding wall and the light shielding member are separated from each other. However, the light shielding wall and the light shielding member may be integrally formed.

  10 optical scanning unit 11, 611, 711, 811, 911 erecting equal-magnification lens array plate, 20 line image sensor, 24 first lens array plate, 24a first lens, 24b second lens, 26 second lens array plate , 26a third lens, 26b fourth lens, 50 first light shielding wall, 52 second light shielding wall, 54 first opening, 56 second opening, 100 image reading device.

Claims (7)

A first lens array plate having a plurality of first lenses regularly arranged on a first surface and a plurality of second lenses regularly arranged on a second surface facing the first surface;
A second lens array plate having a plurality of third lenses regularly arranged on a third surface and a plurality of fourth lenses regularly arranged on a fourth surface opposite to the third surface; Prepared,
The first lens array plate and the second lens array plate are laminated with the second surface and the third surface facing each other so that a pair of corresponding lenses constitutes a coaxial lens system. An erecting equal-magnification lens array plate that receives light from a line-shaped light source on the surface side and forms an erecting equal-magnification image of the line-shaped light source on the image surface on the fourth surface side,
A first light shielding wall erected so as to surround the first lens;
A second light shielding wall erected so as to surround the fourth lens;
A first opening formed on the first lens by the first light shielding wall;
A second opening formed on the fourth lens by the second light shielding wall;
With
An erecting equal-magnification lens array plate, wherein at least one of the first opening and the second opening is formed such that an opening diameter on the lens side is larger than an opening diameter on the opposite side.   2. The erecting equal-magnification lens according to claim 1, wherein at least one of the first opening and the second opening is formed so that an opening diameter on a lens side is larger than a lens diameter. Array plate.   3. The device according to claim 1, wherein at least one of the first opening and the second opening is formed such that an opening diameter decreases in a tapered shape from the lens side toward the opposite side. 4. Erect life-size lens array plate.   4. The erecting apparatus according to claim 1, wherein a light shielding member is provided on at least one of the first surface and the fourth surface so as to cover a region between adjacent lenses. 5. 1x lens array plate.   5. The upright or the like according to claim 1, wherein at least one of the first surface and the fourth surface is subjected to a roughening process in a region between adjacent lenses. Double lens array plate. A line-shaped light source for irradiating light on the read image;
The erecting equal-magnification lens array plate according to any one of claims 1 to 5, which collects light reflected from the read image;
A line image sensor that receives light transmitted through the erecting equal-magnification lens array plate;
An optical scanning unit comprising: An optical scanning unit according to claim 6;
An image processing unit for processing an image signal detected by the optical scanning unit;
An image reading apparatus comprising:

Images