Lens unit, image reading unit, and imaging reading device

Abstract

To form an upright equal magnification image of a subject on an imaging element while deepening the depth of focus.SOLUTION: A lens unit (101) comprises: first lens bodies (105, 106); second lens bodies (109, 110); and a diaphragm member (108) located between the first lens bodies (105, 106) and the second lens bodies (109, 110). The opening width of each of a plurality of openings (108a) of the diaphragm member (108) differs depending on the position of the second lens bodies (109, 110) in the optical axis direction (Z). The position in the optical axis direction (Z) at which the opening width of each of the plurality of openings (108a) becomes minimal coincides with the focus position of each of a plurality of second lenses, and the first lens bodies (105, 106), the diaphragm member (108), and the second lens bodies (109, 110) are arranged so that the image of a subject is formed passing through the second lens bodies (109, 110), the diaphragm member (108), and the first lens bodies (105, 106).SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a lens unit, an image reading unit, and an image reading device. [Background technology]

[0002] There has been a proposal for a lens unit having a subject-side lens array having multiple lenses, an image sensor-side lens array having multiple lenses, and a light shielding plate having multiple openings and arranged between the subject-side lens array and the image sensor-side lens array (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2022-182580 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when an image of a subject is formed on an image sensor through a plurality of lens groups, it is difficult to form an image while increasing the focal depth.

[0005] An object of the present disclosure is to provide a lens unit, an image reading unit, and an image reading device that make it possible to form an image of a subject on an imaging element while increasing the focal depth. [Means for solving the problem]

[0006] The lens unit of the present disclosure comprises a first lens body including a plurality of first lenses arranged in a regular pattern, a second lens body including a plurality of second lenses arranged so as to overlap each of the plurality of first lenses, and an aperture member arranged between the first lens body and the second lens body, the aperture member having a plurality of openings arranged so as to overlap the plurality of first lenses and the plurality of second lenses, wherein an opening width of the opening varies depending on a position in the optical axis direction of the second lens body, the position in the optical axis direction where the opening width is smallest coincides with a focal position of the plurality of second lenses, and the first lens body, the aperture member, and the second lens body are arranged such that an image of a subject is formed through the second lens body, the aperture member, and the first lens body. Effect of the Invention

[0007] According to the device of the present disclosure, it is possible to form an erect life-size image of a subject on an imaging element while increasing the focal depth. [Brief description of the drawings]

[0008] [Figure 1] 1 is an external perspective view illustrating a schematic configuration of an image reading unit according to a first embodiment. [Diagram 2] FIG. 1 is a perspective view (including a cross section) illustrating a schematic configuration of an image reading unit according to a first embodiment. [Diagram 3] 1 is a cross-sectional view illustrating a schematic configuration of a lens unit according to a first embodiment. [Figure 4] 1 is a perspective view (including a cross section) illustrating a schematic configuration of a lens unit according to a first embodiment. [Diagram 5] 5A to 5C are diagrams for explaining the function of the aperture member of the lens unit in accordance with the first embodiment. [Figure 6] 10A and 10B are diagrams for explaining the function of a diaphragm member of a lens unit of a comparative example. [Figure 7] 1A and 1B are diagrams (part 1) for explaining an example of a reading operation of an image reading unit. [Figure 8] 13A and 13B are diagrams (part 2) for explaining an example of a reading operation of the image reading unit. [Figure 9] FIG. 9 is a diagram showing a composite image of the image in FIG. 7(B) and the image in FIG. 8(B). [Figure 10] 13A and 13B are diagrams (part 1) for explaining another example of the reading operation of the image reading unit. [Figure 11] 13A and 13B are diagrams (part 2) for explaining another example of the reading operation of the image reading unit. [Figure 12] FIG. 13 is a diagram showing a composite image of the image in FIG. 10(B) and the image in FIG. 11(B). [Figure 13] FIG. 11 is a perspective view (including a cross section) illustrating a schematic configuration of an image reading unit according to a second embodiment. [Figure 14] FIG. 11 is an exploded perspective view showing a schematic configuration of a lens unit according to a second embodiment. [Figure 15] FIG. 11 is a cross-sectional view illustrating a schematic configuration of a lens unit according to a second embodiment. [Figure 16] 11 is a perspective view (including a cross section) illustrating a schematic configuration of a lens unit according to a second embodiment. FIG. [Figure 17] 10A and 10B are diagrams for explaining the function of the aperture member of the lens unit according to the second embodiment. [Figure 18] FIG. 11 is a diagram showing, as Table 1, specific examples of the lens unit according to the second embodiment. [Figure 19] FIG. 11 is a diagram showing examples of materials of the lens unit according to the second embodiment as Table 2. [Figure 20] FIG. 13 is a perspective view (including a cross section) that illustrates a schematic configuration of an aperture member of a lens unit according to a modified example of the second embodiment. [Figure 21] FIG. 11 is a perspective view (including a cross section) illustrating a schematic configuration of an image reading unit according to a third embodiment. [Figure 22] FIG. 11 is a diagram showing, as Table 3, specific examples of the lens unit according to the third embodiment. [Figure 23]FIG. 13 is a diagram illustrating an outline of a configuration of an image reading device according to a fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] A lens unit according to an embodiment of the present disclosure, an image reading unit having the lens unit and an image sensor, and an image reading device having the image reading unit and a control device will be described below with reference to the drawings. The following embodiments are merely examples, and various modifications are possible within the scope of the present disclosure.

[0010] In the figures, the coordinate axes of an XYZ Cartesian coordinate system are shown to facilitate understanding of the relationships between the figures. The X axis is the coordinate axis in the longitudinal direction of the lens unit (i.e., the X direction). The Y axis is the coordinate axis in the width direction of the lens unit (i.e., the Y direction). The Z axis is the coordinate axis in the optical axis direction of the lens body that constitutes the lens unit (i.e., the Z direction).

[0011] 1. First embodiment 《1-1》Configuration 1 is an external perspective view showing a schematic configuration of an image reading unit 101 according to the first embodiment. The image reading unit 101 is incorporated in an image reading device (described in the fourth embodiment below) and obtains an image of a subject as one-dimensional data along the X direction. The image reading device generates a two-dimensional image of the subject by reading the image while moving the image reading unit 101 or the subject in the Y direction. The image reading unit 101 is configured so that the working distance, i.e., the distance from the upper surface of the image reading unit 101 to the subject, is, for example, 30 mm.

[0012] 2 is a perspective view (including a cross section) that shows a schematic configuration of an image reading unit 101 according to the first embodiment. The image reading unit 101 has a lens unit 112, two rows of image pickup elements 103a and 103b arranged on a substrate 102, a holder 113 as a holding member that holds the lens unit 112 and the substrate 102, and a connector 104 provided on the lower surface of the substrate 102. The lens unit 112 is an optical unit that can form an image of a subject as an erect life-size image on the image pickup elements 103a and 103b.

[0013] FIG. 3 is a cross-sectional view that shows a schematic configuration of the lens unit 112 according to the first embodiment. FIG. 4 is a perspective view (including a cross section) that shows a schematic configuration of the lens unit 112 according to the first embodiment. The lens unit 112 has a first lens array 105 including a plurality of lenses regularly arranged in two rows, and a second lens array 106 including a plurality of lenses regularly arranged in two rows. The lens unit 112 has a first light-shielding member 107 having a plurality of first holes 107a regularly arranged in two rows, and an aperture member 108 having a plurality of openings (i.e., apertures) 108a regularly arranged in two rows. The lens unit 112 also has a third lens array 109 including a plurality of lenses regularly arranged in two rows, a fourth lens array 110 including a plurality of lenses regularly arranged in two rows, and a second light-shielding member 111 having a plurality of second holes 111a regularly arranged in two rows. In the first embodiment, an example is described in which the image reading unit 101 has two rows of image pickup elements 103a and 103b, two rows of lenses in each lens array, two rows of openings 108a (apertures), two rows of first holes 107a in the first light shielding member 107, and two rows of second holes 111a in the second light shielding member 111, but the image pickup elements, the lenses in each lens array, the openings 108a (apertures), the first holes 107a, and the second holes 111a can be arranged in one row, or three or more rows. In particular, two or more rows are preferable in order to suppress visual field defects.

[0014] The first lens array 105, the second lens array 106, the first light-shielding member 107, the aperture member 108, the third lens array 109, the fourth lens array 110, and the second light-shielding member 111 are arranged in a stacked manner from the imaging element side toward the subject side, and these members are held by a holder 113 as a holding member.

[0015] The first lens array 105 and the second lens array 106 constitute a first lens body having a plurality of lenses (also referred to as "first lenses") arranged regularly. The plurality of lenses of the first lens array 105 and the plurality of lenses of the second lens array 106 are arranged so as to overlap each other. The first lens body may be composed of three or more lens arrays. The first lens body may be composed of one lens array, and an example of this case will be described in the third embodiment.

[0016] The third lens array 109 and the fourth lens array 110 constitute a second lens body having a plurality of lenses (also referred to as "second lenses") arranged regularly. The plurality of lenses of the third lens array 109 and the plurality of lenses of the fourth lens array 110 are arranged so as to overlap each other. The second lens body may be composed of three or more lens arrays. The second lens body may be composed of one lens array, and an example of this case will be described in the third embodiment. Here, "so as to overlap" means so that the optical axes coincide with each other.

[0017] The diaphragm member 108 has a plurality of openings 108a arranged so as to overlap with the plurality of first lenses and to overlap with the plurality of second lenses, and is arranged between the first lens body and the second lens body. "So as to overlap" means that the optical axis or the central axis of the openings coincides.

[0018] The opening width (opening diameter in the first embodiment) of each of the multiple openings 108a varies depending on the position in the optical axis direction (Z direction) of the second lens body. The opening width of each of the multiple openings 108a is smallest at a position in the optical axis direction closest to the second lens body (i.e., the position closest to the subject). The opening width of each of the multiple openings 108a is largest at a position in the optical axis direction farthest from the second lens body (i.e., the position closest to the image sensor). The inner wall surface of each of the multiple openings 108a is in a truncated cone shape that gradually widens toward the first lens body. The inner wall surface of each of the multiple openings 108a may be in a stepped shape that gradually widens toward the first lens body.

[0019] In addition, the first lens body, the aperture member 108, and the second lens body are arranged so that the position in the optical axis direction (Z direction) where the opening width of each of the multiple openings 108a is smallest coincides with the focal position of each of the multiple second lenses, and the image of the subject is formed through the second lens body, the aperture member, and the first lens body.

[0020] The substrate 102 is a printed circuit board such as FR-4. On the substrate 102, there are mounted image pickup elements 103a and 103b for converting an optical image formed by an optical system into an image signal, a connector 104 for electrically connecting to an external control device, and various electronic components (not shown) for driving the image pickup elements 103a and 103b. The image pickup elements 103a and 103b are CCD (Charge Coupled Device) line sensors or the like, and generate one-dimensional images. The image pickup elements 103a and 103b are mounted in two rows in the Y direction, each row having an X-direction length of about 10 mm, and are continuously mounted in the X direction. For example, when the reading width is 250 mm, 25 line sensors aligned in the X direction are mounted as the image pickup element 103a, and 25 line sensors aligned in the X direction are mounted as the image pickup element 103b. In the case of the first embodiment, the Y-direction interval between the image pickup elements 103a and 103b is set to 1.732 mm.

[0021] In the lens unit 112, the lenses of the first lens array 105, the lenses of the second lens array 106, the first holes 107a of the first light shielding member 107, the openings 108a of the diaphragm member 108, the lenses of the third lens array 109, the lenses of the fourth lens array 110, and the second holes 111a of the second light shielding member 111 are arranged in two rows in a staggered pattern in the Y direction. In addition, the optical axes of the lenses of the first lens array 105, the optical axes of the lenses of the second lens array 106, the central axes of the first holes 107a of the first light shielding member 107, the central axes of the openings 108a of the diaphragm member 108, the optical axes of the lenses of the third lens array 109, the optical axes of the lenses of the fourth lens array 110, and the central axes of the second holes 111a of the second light shielding member 111 are aligned with each other. As shown in Fig. 3, of the two rows of lenses, openings, and holes aligned in the Y direction and extending in the X direction, the row in the +Y direction is called row La, and the row in the -Y direction is called row Lb. In the first embodiment, the arrangement period of the lenses, openings, and holes is 2 mm apart in the X direction, and the distance between the La row and the Lb row is 1.732 mm. The La row and the Lb row are shifted by 1 mm in the X direction. However, embodiments other than the first embodiment may be used, and for example, the amount of shift in the X direction between the La row and the Lb row may be half or approximately half the arrangement period in the X direction of each row.

[0022] The first to fourth lens arrays 105, 106, 109, and 110 are optical members having lens surfaces formed on both sides. The surface of the lens of the first lens array 105 facing the image pickup element is lens surface 105a, and the surface facing the subject is lens surface 105b. The surface of the lens of the second lens array 106 facing the image pickup element is lens surface 106a, and the surface facing the subject is lens surface 106b. The surface of the lens of the third lens array 109 facing the image pickup element is lens surface 109a, and the surface facing the subject is lens surface 109b. The surface of the lens of the fourth lens array 110 facing the image pickup element is lens surface 110a, and the surface facing the subject is lens surface 110b. The radius, radius of curvature, and aspheric coefficient representing the shape of each lens surface, the distance of each lens surface from the image pickup elements 103a and 103b in the Z direction, and the glass material as the material of each lens array are predetermined.

[0023] The fourth lens array 110 and the third lens array 109 form an inverted reduced image of the subject as an intermediate image, and the second lens array 106 and the first lens array 105 form an inverted enlarged image of the intermediate image, so that an erect life-size image of the subject is formed on the image pickup elements 103a and 103b. The first lens array 105 and the third lens array 109 have negative refractive power, and the second lens array 106 and the fourth lens array 110 have positive refractive power. It is desirable that the second lens array 106 has a larger Abbe number than the first lens array 105, the fourth lens array 110 has a larger Abbe number than the third lens array 109, and the refractive power of the optical system consisting of the first lens array 105 and the second lens array 106 is larger than the optical system consisting of the third lens array 109 and the first lens array 105. Moreover, it is desirable that the diameter of the lens surface 110b of the fourth lens array 110 is 50% or more of the arrangement period of the lens surface in the X direction. In the first embodiment, a configuration having four lens arrays has been described, but the present invention is not limited to such a configuration. An optical system that can be used in the first embodiment may be an optical system that is composed of at least two lens arrays, forms an inverted reduced image of a subject as an intermediate image, and forms an inverted enlarged image of the intermediate image to form an erect life-size image of the subject on the image pickup elements 103a and 103b.

[0024] The aperture member 108 has a plurality of truncated cone-shaped openings 108a formed in an array. In the first embodiment, the opening width of the opening 108a is, for example, 1 mm on the larger side and 0.2 mm on the smaller side, and the thickness is 1 mm. The Z-direction position of the opening end on the smaller side is arranged at the position where the parallel light from the subject passes through the third lens array 109 and the fourth lens array 110 and is condensed, that is, the focal position on the image sensor side. By arranging the aperture at the focal position on the image sensor side of the optical system consisting of the combination of the third lens array 109 and the fourth lens array 110, the lens unit 112 becomes an optical system that is telecentric on the object side. The aperture member 108 uses black polycarbonate in order to match the linear expansion coefficient with each lens array. When the material of each lens array is glass, the aperture member 108 may be a metal such as aluminum painted black in order to match the linear expansion coefficient. The size of the opening 108a may be within the period of the array on the larger side, but it is desirable that the smaller side (i.e., the minimum value) is 25% or less of the diameter of the fourth lens array 110. The thickness may be any thickness that can be manufactured. In this embodiment, the diameter of the opening 108a is the opening width, and this opening width is the width of the opening in the X direction, which is the direction in which the lenses are arranged in the lens array. In this embodiment, the opening diameter of the opening cross section in the XY plane is shown.

[0025] The first light shielding member 107 has first holes 107a, which are cylindrical openings, formed in an array. The opening width of the first holes 107a in the first embodiment is 0.6 mm, the thickness is 1 mm, and the position in the Z direction is a position where the end face on the imaging element side is 0.2 mm away from the apex of the lens surface 106b in the +Z direction. The second light shielding member 111 has second holes 111a, which are cylindrical openings, formed in an array. The opening width of the second holes 111a in the first embodiment is 1.2 mm, the thickness is 1 mm, and the position in the Z direction is a position where the end face on the imaging element side is 0.1 mm away from the apex of the lens surface 110b in the +Z direction. The first light shielding member 107 and the second light shielding member 111 use black polycarbonate to match the linear expansion coefficient with each lens array. When the material of the lens array is glass, it may be a metal such as aluminum painted black in order to match the linear expansion coefficient. The number, arrangement, and opening width of the light shielding members may be any combination other than that of the first embodiment as long as it satisfies the following conditions. As shown in FIG. 5, the arrangement may be such that light incident on the lens surface 110b of the fourth lens array 110 can block light emitted from a lens surface having an optical axis deviated from the optical axis of the lens surface on which the light is incident, such as light emitted from the lens surface 109a of the third lens array 109 or the lens surface adjacent thereto. Also, if the effect of stray light formed on the image sensor surface by light emitted from a position outside the optical axis of the incident light can be ignored due to the required quality of the image reading device, the light shielding members may not be arranged. Also, when the light shielding members are arranged on the subject side of the fourth lens array 110, the opening width of the light shielding members is at least half the arrangement period in the X direction.

[0026] FIG. 5 is a diagram for explaining the function of the diaphragm member 108 of the lens unit 112 according to the first embodiment. FIG. 6 is a diagram for explaining the function of the diaphragm member 508 of the lens unit of the comparative example. As shown in FIG. 5, the opening 108a of the diaphragm member 108 has a truncated cone-shaped inner wall surface, and the portion 108b with the smallest opening width is located on the most subject side of the diaphragm member 108. In this case, the light L0 traveling in the optical axis direction from the subject passes through the opening 108a and heads toward the first hole 107a of the first light blocking member 107, but the light L1 traveling in a direction inclined to the optical axis direction does not head toward the first hole 107a (i.e., is blocked). In contrast, when the opening 508a of the diaphragm member 508 has a cylindrical inner wall surface as shown in FIG. 6, the light L2 traveling in a direction inclined to the optical axis direction heads toward the first hole 107a as stray light reflected by the inner wall surface, so that the stray light incident on the imaging element may increase. As shown in Fig. 5, according to the first embodiment, it is possible to reduce stray light reaching the imaging elements 103a and 103b. In Fig. 5, it is preferable to set the inclination angle θ of the inner wall surface of the truncated cone to a range of 30° to 80°.

[0027] The lens unit 112 is aligned to the position described above and fixed with an adhesive (not shown). The holder is a member such as a metal plate that supports the substrate 102 and the lens unit 112. The substrate 102 and the lens unit 112 are placed in a predetermined position and fixed with an adhesive.

[0028] 《1-2》Operation The operation of each component will be described. First, light from a subject is collected by an optical system consisting of the fourth lens array 110 and the third lens array 109 to form an inverted and reduced intermediate image. At this time, the fourth lens array 110 has a positive refractive power, the third lens array 109 has a negative refractive power, and the third lens array 109 has a smaller Abbe number than the fourth lens array 110, so that the wavelength aberration of light from the subject can be corrected. The light from the subject is narrowed by the aperture member 108 at the focal position on the imaging element side of the optical system consisting of the fourth lens array 110 and the third lens array 109, so that light incident on the fourth lens array 110 in a direction other than the optical axis direction can be cut. The first light shielding member 107 and the second light shielding member 111 prevent light incident on each lens surface from being incident on a lens surface off the optical axis. An optical system consisting of the second lens array 106 and the first lens array 105 inverts and enlarges an inverted, reduced intermediate image of the subject, forming an erect, life-size image on the image pickup elements 103a and 103b. At this time, the second lens array 106 has a positive refractive power, the first lens array 105 has a negative refractive power, and the first lens array 105 has a smaller Abbe number than the second lens array 106, so that it is possible to correct wavelength aberration of light from the intermediate image.

[0029] Next, an image reading method in the first embodiment will be described. FIGS. 7(A) and (B) and FIGS. 8(A) and (B) are diagrams for explaining an example of the reading operation of the image reading unit 101. FIG. 9 is a diagram showing a composite image of the image in FIG. 7(B) and the image in FIG. 8(B). A case of reading an image of a character string "ABCDEF" written as shown in FIGS. 7(A) and 8(A) will be described. In the first embodiment, since each optical system is a telecentric optical system on the object side, the field of view that can be imaged is limited to the second hole 111a of the second light shielding member 111. Also, since the imaging elements 103a and 103b are one-dimensional line sensors, the area that can be imaged is limited to the area where the second hole 111a of the second light shielding member 111 and the imaging elements 103a and 103b shown in FIG. 7(A) overlap. That is, only the area painted gray in FIG. 7(B) is imaged by the imaging element 103a. The area outside the second hole 111a is not imaged, and the field of view is missing. Here, FIG. 8(A) shows a state in which the image reading unit 101 or the subject is scanned in the Y direction and moved by the Y-direction interval of the image pickup elements 103a and 103b. In FIG. 8(A), the image pickup element 103b moves to the position where the image pickup element 103a was in FIG. 7(A). In the state of FIG. 8(A), the area imaged by the image pickup element 103b is shown by the area filled in gray in FIG. 8(B). As in FIG. 7(B), the area outside the second hole 111a is not imaged, and the field of view is missing. However, the optical axes of the La and Lb rows are shifted by half the period in the X direction, so that the La and Lb rows have a relationship in which their fields of view are complementary to each other. Therefore, by synthesizing the image captured by the image sensor 103a with the image captured by the image sensor 103b after scanning the Y-direction interval between the La and Lb rows, an image without loss of field of view can be obtained. In addition, since the optical system forms an erect life-size image, there is no need to invert the images when synthesizing them, and a simple calculation of adding them together is sufficient.

[0030] Since lens unit 112 is an optical system that forms an erect life-size image, it is only necessary to pay attention to the alignment of lens unit 112 and image pickup elements 103a and 103b in the Y direction at the time of shipment, and there is no need to align them to a specific position in the X direction.

[0031] 10(A) and (B) and 11(A) and (B) are diagrams for explaining another example of the reading operation of the image reading unit. FIG. 12 is a diagram showing a composite image of the image in FIG. 10(B) and the image in FIG. 11(B). In addition, when resin is used as the material of the lens unit 112, the linear expansion coefficient difference with the substrate is large, so that the positional relationship in the X direction between the image pickup elements 103a and 103b and the lens unit 112 may differ between the time of shipment and the time of operation. FIG. 10(A) and (B) and FIG. 11(A) and (B) show an example in which the lens unit 112 is shifted in the X direction with respect to the image pickup elements 103a and 103b. Even in such a case, since the lens unit 112 is an optical system that forms an erect life-size image, it is possible to obtain the same image as that shown in FIG. 7(A) and (B) and FIG. 8(A) and (B) by simply adding the images together without performing any calculation based on the amount of shift. In other words, even if lens unit 112 has a period that forms multiple discontinuous images for the size of one image sensor 103a, 103b, the image can be formed by a simple addition operation, so that the diameter of each lens surface can be made smaller than that of image sensors 103a, 103b. In other words, the size of image reading unit 101 in the Y direction can be made smaller.

[0032] When the subject moves in the Z direction, the subject does not expand or shrink because lens unit 112 is an object-side telecentric optical system. Therefore, even if the subject moves in the Z direction, there is no shift in the position where the subject image is formed on image sensors 103a and 103b, so there is no position shift when the images of image sensors 103a and 103b are combined, and the depth of field does not decrease.

[0033] Since the optical system consisting of the first lens array 105 and the second lens array 106 has a greater refractive power than the optical system consisting of the third lens array 109 and the first lens array 105, the distance from the lens surface 105a to the image pickup elements 103a and 103b can be set shorter than the working distance, and the size of the image reading unit 101 in the Z direction can be reduced. Generally, the greater the working distance, the deeper the depth of field. With this configuration, there is little need to increase the size of the image reading unit 101 in the Z direction even if the working distance is extended, that is, the depth of field is deepened.

[0034] 1-3 Effects As described above, according to the first embodiment, the image reading unit 101 is configured with an optical system that forms an erect life-size image that is telecentric on the object side, which is composed of a combination of a plurality of lens arrays integrally molded in a staggered pattern in two rows and a light blocking member and diaphragm member 108 integrally molded in a staggered pattern in two rows whose optical axis is aligned with that of the lens array, and an array of image pickup elements 103a, 103b arranged in two rows in accordance with the positions of each row of the optical system, and has the effect of expanding the depth of field of a CIS (Contact Image Sensor) with only a simple calculation, without sacrificing loss of field of view, ease of assembly, or size.

[0035] 2. Second embodiment 2-1. Configuration FIG. 13 is a perspective view (including a cross section) that shows a schematic configuration of the image reading unit 201 according to the second embodiment. FIG. 14 is an exploded perspective view that shows a schematic configuration of the lens unit 212 according to the second embodiment. FIG. 15 is a cross section that shows a schematic configuration of the lens unit 212 according to the second embodiment. FIG. 16 is a perspective view (including a cross section) that shows a schematic configuration of the lens unit 212 according to the second embodiment. The image reading unit 201 according to the second embodiment is different from the image reading unit 101 according to the first embodiment in the shape of the opening 208a of the diaphragm member 208. In the second embodiment, the opening 208a of the diaphragm member 208 is a truncated cone shape that has a minimum opening width (opening diameter in the second embodiment) on the imaging element side. Other than this point, the second embodiment is similar to the first embodiment.

[0036] In embodiment 2, the substrate 202, the imaging elements 203a, 203b, the first lens array 205, the second lens array 206, the first light-shielding member 207, the third lens array 209, the fourth lens array 210, and the second light-shielding member 211 are similar to the substrate 102, the imaging elements 103a, 103b, the first lens array 105, the second lens array 106, the first light-shielding member 107, the third lens array 109, the fourth lens array 110, and the second light-shielding member 111 in embodiment 1.

[0037] FIG. 17 is a diagram for explaining the function of the diaphragm member 208 of the lens unit 212 according to the second embodiment. As shown in FIG. 17, the opening 208a of the diaphragm member 208 has a truncated cone-shaped inner wall surface, and the portion 208b with the smallest opening width is located closest to the image sensor side of the diaphragm member 208. In this case, the light L0 traveling in the optical axis direction from the subject passes through the opening 208a, heads toward the first hole 207a of the first light blocking member 207, and is detected. In contrast, the light L3 traveling in a direction inclined to the optical axis direction does not head toward the first hole 307a. As shown in FIG. 17, according to the second embodiment, the stray light reaching the image sensors 203a and 203b can be reduced. In FIG. 17, the inclination angle θ of the truncated cone-shaped inner wall surface is desirably set within a range of 30° to 80°.

[0038] FIG. 18 is a diagram showing a specific example of lens unit 212 according to embodiment 2 as Table 1. First to fourth lens arrays 205, 206, 209, 210 are lens arrays having lens surfaces formed on both sides. The surface of the lens of first lens array 205 facing the image sensor is lens surface 205a, and the surface of the lens facing the subject is lens surface 205b. The surface of the lens of second lens array 206 facing the image sensor is lens surface 206a, and the surface of the lens facing the subject is lens surface 206b. The surface of the lens of third lens array 209 facing the image sensor is lens surface 209a, and the surface of the lens facing the subject is lens surface 209b. The surface of the lens of fourth lens array 210 facing the image sensor is lens surface 210a, and the surface of the lens facing the subject is lens surface 210b. The radius [mm], radius of curvature r [mm], and aspheric coefficients A, B, and C that represent the shape of each lens surface, and the distance Z in the Z direction from the image sensor of each lens surface can be calculated from the following formula using the values ​​in Table 1 shown in FIG.

[0039]

number

[0040] 19 is a diagram showing specific examples of the lens unit 212 according to the embodiment 2 as Table 2. As the glass materials which are the materials of the first to fourth lens arrays 205, 206, 209, and 210, those shown in Table 2 of FIG.

[0041] Fig. 20 is a perspective view (including a cross section) that shows a schematic configuration of diaphragm member 218 of lens unit 212 according to a modified example of embodiment 2. In the example of Fig. 20, aperture 218a of diaphragm member 218 has a stepped inner wall surface, and portion 218b where the opening width is smallest is located closest to the imaging element side of diaphragm member 218. When diaphragm member 218 having such a shape is used, it has the same function as the case shown in Fig. 17.

[0042] 《2-2》Operation The operation of the second embodiment is similar to that of the first embodiment.

[0043] 2-3 Effects As described above, according to the second embodiment, the image reading unit 201 is configured with an optical system that forms an erect, life-size image that is telecentric on the object side, which is composed of a combination of a plurality of lens arrays integrally molded in a staggered pattern in two rows, a light-shielding member integrally molded in a staggered pattern in two rows whose optical axis is aligned with that of the lens array, and an aperture member 208, and an array of image pickup elements 203a, 203b arranged in two rows in accordance with the positions of each row of this optical system, and has the effect of being able to expand the depth of field of the CIS with only a simple calculation, without sacrificing loss of field of view, ease of assembly, or size.

[0044] Furthermore, since the composite focal position of the third lens array 209 and the fourth lens array 210 is aligned with the end of the opening 208a on the imaging element side (the part 208b where the opening width is smallest), the size in the Z direction can be made smaller than in the case of embodiment 1.

[0045] 3. Third embodiment FIG. 21 is a perspective view (including a cross section) that shows a schematic configuration of an image reading unit 301 according to the third embodiment. The image reading unit 301 has a lens unit 312 and an image sensor 303 (in FIG. 21, image sensors 303a in a first row and image sensors 303b in a second row). The lens unit 312 is an optical unit that enables an image of a subject to be formed on the image sensor 303 as an erect life-size image. The lens unit 312 has a lens array 306 as a first lens body having a plurality of regularly arranged first lenses, and a lens array 310 as a second lens body having a plurality of second lenses arranged so as to overlap the plurality of first lenses, and forming an image that has passed through the lens array 306. In addition, the lens unit 312 has a plurality of openings 308a arranged so as to overlap the plurality of first lenses and the plurality of second lenses, and has an aperture member 308 arranged between the first lens body (lens array 306) and the second lens body (lens array 310).

[0046] The opening width of each of the plurality of openings 308a varies depending on the position in the optical axis direction of the second lens body 310. Furthermore, the lens array 306 as the first lens body, the aperture member 308, and the second lens array 310 as the second lens body are arranged so that the position in the optical axis direction at which each of the plurality of openings 308a has a minimum opening width coincides with the focal position of each of the plurality of second lenses.

[0047] FIG. 22 is a diagram showing a specific example of the lens unit 312 according to the third embodiment as Table 3. In the second embodiment, the lens arrays have different shapes, but the same shape of lens arrays may be used by inverting them. However, as in the second embodiment, the optical system must form an inverted reduced image of the subject as an intermediate image, and form an inverted enlarged image of the intermediate image to form an erect life-size image of the subject on the imaging element. As shown in FIG. 22, the radius, curvature radius, aspheric coefficient, and Z-direction distance from the imaging element of each lens surface in the third embodiment may be set. In addition, the APL5514ML described in the second embodiment may be used as the glass material constituting the lens array.

[0048] As described above, in the third embodiment, by using two lens arrays of the same shape, each of which is inverted, it is possible to reduce the number of types of materials and reduce costs.

[0049] 4. Fourth embodiment 23 is a diagram showing a schematic configuration of an image reading device 10 according to the fourth embodiment. The image reading device 10 has the image reading unit 101, a control device 117 as a control unit that synthesizes a plurality of images read by the image reading unit 101, and a cable 116 that connects the image reading unit 101 and the control device 117. The control device 117 is configured by an arithmetic circuit that executes various calculations or a processor that executes a software program. The control device 117 may be a computer. The image reading unit 101 may be replaced with another image reading unit 201 or 301 described in the first to third embodiments.

[0050] In the image reading device 10, the image reading unit 101 reads the inspection object 114 as a subject conveyed at a constant speed by a conveying system 115 such as a belt conveyor, and performs an appearance inspection such as whether the inspection object 114 has scratches and whether the dimensions of the inspection object 114 are within a standard range. The inspection object 114 is, for example, an instrument, a semiconductor instrument, an electric instrument, various parts, a product, etc. First, a lighting device (not shown) irradiates the inspection object 114 with light, and an erect life-size image of the inspection object 114 is formed on the image pickup elements 103a and 103b (FIG. 2). The image pickup elements 103a and 103b (FIG. 2) convert the light image of the inspection object 114 into an image signal. The image signal is sent to the control device 117 via a cable 116 connected to the connector 104, and the control device 117 performs a synthesis process of the image. The control device 117 can perform an appearance inspection, a dimensional inspection, etc. of the inspection object 114 using the image generated by the synthesis process.

[0051] The control device 117 may control the operation of the transport system 115 and a lighting device (not shown). The transport system 115 may be a mechanism for moving the image reading unit 101. [Explanation of symbols]

[0052] 10 Image reading device, 101, 201, 301 Image reading unit, 102, 202, 302 Board, 103, 103a, 103b, 203, 203a, 203b, 303, 303a, 303b Imaging element, 104 Connector, 105, 205 First lens array (first lens body), 106, 206 Second lens array (first lens body), 107, 207, 307 First light blocking member, 108, 208, 308 Aperture member, 108a, 208a, 308a Opening, 109, 209 Third lens array (second lens body), 110, 210 Fourth lens array (second lens body), 111, 211, 307 Second light-shielding member, 112, 212, 312 lens unit, 113, 213, 313 holder, 117 control device, 305 third light-shielding member, 306 lens array (first lens body), 310 lens array (second lens body).

Claims

1. a first lens body including a plurality of regularly-arranged first lenses; a second lens body including a plurality of second lenses arranged so as to overlap the plurality of first lenses; a diaphragm member having a plurality of openings arranged to overlap the plurality of first lenses and the plurality of second lenses, the diaphragm member being arranged between the first lens body and the second lens body; Equipped with an opening width of the opening portion varies depending on a position of the second lens body in an optical axis direction; The first lens body, the diaphragm member, and the second lens body are arranged so that a position in the optical axis direction at which the aperture width is smallest coincides with focal positions of the plurality of second lenses, and an image of an object is formed through the second lens body, the diaphragm member, and the first lens body. A lens unit characterized by:

2. The aperture width is smallest at a position in the optical axis direction closest to the second lens body.

2. The lens unit according to claim 1.

3. The aperture width is maximum at a position in the optical axis direction farthest from the second lens body.

3. The lens unit according to claim 2.

4. The inner wall surfaces of the plurality of openings are in a truncated cone shape or a stepped shape that widens toward the first lens body.

4. The lens unit according to claim 3.

5. The aperture width is smallest at a position in the optical axis direction farthest from the second lens body.

2. The lens unit according to claim 1.

6. The aperture width is maximum at a position in the optical axis direction closest to the second lens body.

6. The lens unit according to claim 5.

7. The inner wall surfaces of the plurality of openings have a truncated cone shape or a stepped shape that narrows toward the first lens body.

7. The lens unit according to claim 6.

8. The minimum value of the opening width is 25% or less of the diameter of the first lenses.

8. The lens unit according to claim 1, wherein the first lens is a lens unit having a first surface and a second surface.

9. The refractive power of the first lenses is greater than the refractive power of the second lenses.

8. The lens unit according to claim 1, wherein the first lens is a lens unit having a first surface and a second surface.

10. The minimum value of the aperture width is greater than the diameter of the second lenses.

8. The lens unit according to claim 1, wherein the first lens is a lens unit having a first surface and a second surface.

11. the first lens body having one or more lens arrays; The second lens body includes one or more lens arrays.

8. The lens unit according to claim 1, wherein the first lens is a lens unit having a first surface and a second surface.

12. the first lens body has a first lens array and a second lens array arranged to overlap in the optical axis direction, The second lens body has a third lens array and a fourth lens array arranged to overlap in the optical axis direction.

8. The lens unit according to claim 1, wherein the first lens is a lens unit having a first surface and a second surface.

13. each of the first lens array and the third lens array has a negative refractive power; Each of the second lens array and the fourth lens array has a positive refractive power.

13. The lens unit according to claim 12.

14. the Abbe number of the first lens array is smaller than the Abbe number of the second lens array; The lens unit according to claim 12 , wherein the Abbe number of the third lens array is smaller than the Abbe number of the fourth lens array.

15. The image of the subject passes through the second lens body, the aperture member, and the first lens body to form an erect life-size image.

8. The lens unit according to claim 1, wherein the first lens is a lens unit having a first surface and a second surface.

16. A lens unit according to any one of claims 1 to 7; a plurality of image pickup elements on which the image of the subject is formed by the lens unit; An image reading unit comprising:

17. An image reading unit according to claim 16; a control device that generates a two-dimensional image from images read by the plurality of image pickup elements of the image reading unit; 1. An image reading device comprising:

Images