PICTURE READING DEVICE

Abstract

Image reading device (100, 110, 120, 130, 200, 300, 400), including: a plurality of light-receiving pixels (10) arranged in a predetermined orientation and configured to receive light reflected from an imaging object (6), wherein the imaging object (6) is placed on a predetermined reference surface (S); a first light-shielding element (11) having a plurality of first openings (31) and arranged between the plurality of light-receiving pixels (10) and the reference surface (S); a second light-shielding element (12) having a plurality of second openings (32) and arranged between the plurality of first openings (31) and the reference surface (S); a plurality of condenser lenses (14) arranged between the plurality of second apertures (32) and the reference surface (S) and arranged at a distance from the plurality of second apertures (32), a first translucent element (51) arranged between the first light-blocking element (11) and the second light-blocking element (12); and a second light-transmitting element (52) arranged between the second light-shielding element (12) and the plurality of condenser lenses (14); wherein the multitude of first openings (31) are arranged such that they each correspond to the multitude of light-receiving pixels (10), the multitude of second openings (32) are arranged such that each corresponds to the multitude of light-receiving pixels (10), the multitude of condenser lenses (14) are arranged such that each corresponds to the multitude of light-receiving pixels (10), the plurality of condenser lenses (14), the second light-shielding element (12), the first light-shielding element (11) and the plurality of light-receiving pixels (10) are arranged at positions where the reflected light entering each light-receiving pixel (10) of the plurality of light-receiving pixels (10) successively passes through one of the plurality of condenser lenses (14) corresponding to the respective light-receiving pixel (10), one of the plurality of second apertures (32) corresponding to the respective light-receiving pixel (10), and one of the plurality of first apertures (31) corresponding to the respective light-receiving pixel (10), and enters the respective light-receiving pixel (10), and t 2 > n ⋅ t 0 − t 1 where t0 denotes a distance between the plurality of light-receiving pixels (10) and the first light-shielding element (11), t1 denotes a thickness of the first light-transmitting element (51), t2 denotes a thickness of the second light-transmitting element (52), and n denotes a refractive index of each of the first light-transmitting element (51) and the second light-transmitting element (52).

Description

AREA OF TECHNOLOGY

[0001] The present invention relates to an image reading device. STATE OF THE ART

[0002] A proposed image reading device comprises a light-shielding element having an aperture through which reflected light, reflected from an imaging object, passes, and a plurality of light-receiving pixels (i.e., light-receiving devices) into which reflected light, having passed through the aperture, enters. Reference is made in this regard to JP 2015-133658 A. JP S63-156473 A discloses an image sensor having a plurality of light-receiving elements and a plurality of lenses, further comprising an optical cylinder between the respective light-receiving element and the lens to prevent stray light. SUMMARY OF THE INVENTION; PROBLEM TO BE SOLVED BY THE INVENTION

[0003] However, the image reading device described in JP 2015-133658 A has the problem that the depth of field decreases when the aperture is enlarged to increase the amount of light received by light-receiving pixels.

[0004] The present invention was made to solve the above-mentioned problems and has the objective of providing an image reading device that is able to increase the depth of field while increasing the amount of light received by light-receiving pixels. MEANS TO SOLVENT THE PROBLEM

[0005] An image reading device according to one aspect of the present invention comprises: a plurality of light-receiving pixels arranged in a predetermined orientation and configured to receive light reflected from an imaging object, the imaging object being placed on a predetermined reference surface; a first light-shielding element having a plurality of first apertures and arranged between the plurality of light-receiving pixels and the reference surface; a second light-shielding element having a plurality of second apertures and arranged between the plurality of first apertures and the reference surface; and a plurality of condenser lenses arranged between the plurality of second apertures and the reference surface and spaced apart from the plurality of second apertures, the plurality of first apertures being arranged such thatthat these each correspond to the plurality of light-receiving pixels, the plurality of second apertures are arranged such that they each correspond to the plurality of light-receiving pixels, the plurality of condenser lenses are arranged such that they each correspond to the plurality of light-receiving pixels, and the plurality of condenser lenses, the second light-shielding element, the first light-shielding element, and the plurality of light-receiving pixels are arranged at positions where the reflected light entering each light-receiving pixel of the plurality of light-receiving pixels successively passes through one of the plurality of condenser lenses corresponding to the respective light-receiving pixel, one of the plurality of second apertures corresponding to the respective light-receiving pixel, and one of the plurality of first apertures corresponding to the respective light-receiving pixel....and enters the respective light-receiving pixel. The image reading device comprises a first light-transmitting element arranged between the first light-blocking element and the second light-blocking element, and a second light-transmitting element arranged between the second light-blocking element and the plurality of condenser lenses. Furthermore, t2>n⋅t0−t1, where t0 denotes a distance between the plurality of light-receiving pixels and the first light-shielding element, t1 denotes a thickness of the first light-transmitting element, t2 denotes a thickness of the second light-transmitting element, and n denotes a refractive index of each of the first light-transmitting element and the second light-transmitting element. IMPACT OF THE INVENTION

[0006] According to the present invention, it is possible to increase the depth of field and simultaneously increase the amount of light received by the light-receiving pixels. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a perspective view schematically representing a main configuration of an image reading device according to a first embodiment of the present invention. Fig. 2 is a sectional view of the Fig. 1. Image reading device shown along section line A2-A2. Fig. 3 is a sectional view of the Fig. 1. Image reading device shown along section line A3-A3. Fig. Figure 4 is a top view showing part of an imaging sensor unit, comprising a multitude of Fig. 1 light-receiving pixels shown. Fig. 5 is a diagram that shows a configuration of a Fig. Figure 1 schematically represents the optical lighting unit shown and the illuminating light emitted by the optical lighting unit. Fig. 6 is a diagram that shows part of the information in Fig. The configuration shown in Figure 3 and the reflected light passing through the second and first openings are shown. Fig. 7A and Fig. Figure 7B are diagrams describing a condition that reflected light, which has passed through the second apertures and first apertures corresponding to light-receiving pixels, enters the light-receiving pixels in the image reading device according to the first embodiment. Fig. 8 is a sectional view of the Fig. 1. Image reading device shown along section line A8-A8. Fig. Figure 9 is a diagram that schematically illustrates the entry of reflected light into a light-receiving pixel in an image reading device according to a first comparative example. Fig. Figure 10 is a diagram showing backlighting as imaginary light beams moving from a light-receiving pixel in a +Z-axis direction in the image reading device according to the first comparison example. Fig. 11 is a diagram showing the spread of in Fig. The 10 depicted backlighting shows. Fig. Figure 12 is a diagram that schematically illustrates the entry of reflected light into a light-receiving pixel in an image reading device according to a second comparative example. Fig. Figure 13 is a diagram showing imaginary backlighting moving from a light-receiving pixel in the +Z-axis direction in the image reading device according to the second comparison example. Fig. 14 is a diagram showing the spread of the in Fig. 13 depicted backlighting. Fig. Figure 15 is a diagram that schematically represents reflected light entering the light-receiving pixel in the image reading device according to the first embodiment. Fig. Figure 16 is a diagram showing imaginary backlighting moving from the light-receiving pixel in the +Z-axis direction in the image reading device according to the first embodiment. Fig. 17 is a diagram showing the spread of the in Fig. 16 depicted backlight beams. Fig. Figure 18 is a diagram showing imaginary backlighting from the light-receiving pixel in the +Z-axis direction in the image reading device according to the first embodiment in a case where one of the first apertures or the second aperture is an aperture stop. Fig. Figure 19 is a diagram showing imaginary backlighting moving from a light-receiving pixel in the +Z-axis direction in an image reading device according to a third comparative example. Fig. Figure 20 is a diagram showing imaginary backlight moving from the light-receiving pixel in the +Z-axis direction in the image reading device according to the first embodiment in a case where the first aperture is an aperture diaphragm. Fig. Figure 21A is a diagram showing imaginary backlighting moving from a light-receiving pixel in the +Z-axis direction in an image reading device according to a fourth comparative example, and Fig. Figure 21B is a diagram showing imaginary backlighting extending from a light-receiving pixel in the +Z-axis direction in an image reading device according to a fifth comparative example. Fig. 22A is a diagram that moves imaginary backlighting moving from the light-receiving pixel in the +Z-axis direction in the image reading device according to the first embodiment, and Fig. Figure 22B is a diagram showing imaginary backlighting moving from a light-receiving pixel in the +Z-axis direction in an image reading device according to a variant of the first embodiment. Fig. Figure 23 is a diagram showing imaginary backlighting moving from a light-receiving pixel in a +Z-axis direction in an image reading device according to a variant of the first embodiment. Fig. Figure 24 is a perspective view that schematically represents a configuration of an optical imaging unit of the image reading device according to the variant of the first embodiment. Fig. Figure 25 is a diagram showing the reflected light entering the light-receiving pixel, in the Fig. 24 schematically represents the image reading device shown. Fig. Figure 26 is a perspective view that schematically represents a configuration of an optical imaging unit of an image reading device according to a second embodiment. Fig. Figure 27 is a perspective view that schematically represents a configuration of an optical imaging unit of an image reading device according to a third embodiment. Fig. Figure 28 is a perspective view that schematically represents a configuration of an optical imaging unit of an image reading device according to a fourth embodiment. TYPE AND METHOD OF EXECUTION OF THE INVENTION

[0007] Image reading devices according to embodiments of the present invention are described below with reference to the drawings. The following embodiments are merely examples, and various modifications can be made within the scope of protection of the present invention.

[0008] The figures show the coordinate axes of an orthogonal XYZ coordinate system to facilitate understanding of the description. The X-axis is a coordinate axis parallel to the main scanning direction of an image reader. The Y-axis is a coordinate axis parallel to a sub-scanning direction of the image reader. The Z-axis is a coordinate axis orthogonal to both the X-axis and the Y-axis. FIRST VERSION Configuration of the image reading device

[0009] Fig. Figure 1 is a perspective view that schematically represents a main configuration of an image reading device 100 according to a first embodiment. Fig. 2 is a sectional view of the Fig. 1. Image reading device shown 100 along section line A2-A2. Fig. 3 is a sectional view of the Fig. 1. Image reading device shown 100 along the A3-A3 section line. As shown in the Fig. As shown in Figures 1 to 3, the image reading device 100 comprises an optical imaging unit 1, an optical illumination unit 2, and an upper glass plate 7 serving as a document support table. When illumination 25 is emitted from the optical illumination unit 2 onto a document 6, which serves as the imaging object and is placed on the upper glass plate 7, the illumination 25 is reflected off the document 6 and serves as reflected light. The reflected light is received by the optical imaging unit 1, allowing image information from the document 6 to be read. In the first embodiment, in order for the optical imaging unit 1 to acquire two-dimensional image information from the document 6, the document 6 is conveyed by a conveyor (not shown) along the upper glass plate 7 in a sub-scanning direction (i.e., Y-axis direction) orthogonal to a main scanning direction (i.e., X-axis direction).Accordingly, the entire document 6 can be scanned. Scanning the entire document 6 can be performed by moving the optical imaging unit 1 in the Y-axis direction, while the document 6 remains stationary.

[0010] Document 6 is an example of an imaging object that is detected by the optical imaging unit 1. Document 6 is, for example, a printed material on which characters, images, or the like are printed. Document 6 is placed on a predetermined reference surface S. The reference surface S is the surface onto which Document 6 is placed, that is, the surface on the upper glass plate 7. The upper glass plate 7 is located between Document 6 and the optical imaging unit 1. The upper glass plate 7 has a thickness of, for example, 1.0 mm. The configuration with the reference surface S onto which Document 6 is placed is not limited to the upper glass plate 7.

[0011] The optical imaging unit 1 comprises a plurality of light-receiving pixels 10, a first light-shielding element 11 having a plurality of first apertures 31, a second light-shielding element 12 having a plurality of second apertures 32, a third light-shielding element 13 having a plurality of third apertures 33 and a plurality of condenser lenses 14.

[0012] Fig. Figure 4 is a top view showing part of the imaging sensor unit 3, comprising the multitude of light-receiving pixels 10. As shown in the Fig. 1 and Fig. As shown in Figure 4, the plurality of light-receiving pixels 10 are contained within an image sensor chip 8. The image sensor chip 8 is mounted on an image sensor board 9. The image sensor board 9 is a mounting board made of an opaque element. The plurality of light-receiving pixels 10 are arranged in the X-axis direction, which is a predetermined orientation. The plurality of light-receiving pixels 10 comprises a first row 8a of light-receiving pixels 10 oriented in the X-axis direction and a second row 8b of light-receiving pixels 10 oriented in the X-axis direction. The light-receiving pixels 10 receive light reflected from the document 6. For example, the size of a light-receiving area of ​​a single light-receiving pixel 10 is 63 µm × 63 µm.The distance p in the X-axis direction between the center positions of the light-receiving pixels 10 adjacent to each other in the X-axis direction is, for example, 252 µm. The distance q in the Y-axis direction between the center positions of the light-receiving pixels 10 is, for example, 252 µm. In . Fig. In Figure 4, the multitude of light-receiving pixels 10 are arranged in an offset pattern. Specifically, the second row 8b of light-receiving pixels 10 is shifted in the X-axis direction by a distance p / 2 of 1 / 2 of the distance p from the adjacent first row 8a of light-receiving pixels 10. Accordingly, each of the light-receiving pixels 10 in the second row 8b is located at an intermediate position in the X-axis direction between the adjacent light-receiving pixels 10 in the first row 8a of light-receiving pixels 10.

[0013] As in the Fig. As shown in Figures 1 to 3, the first light-shielding element 11 is arranged between the plurality of light-receiving pixels 10 and the reference surface S. The first light-shielding element 11 has a plurality of first apertures 31 through which the light reflected from the document 6 passes. A portion of the first light-shielding element 11, excluding the first apertures 31, is a first light-shielding section 41 that blocks reflected light. The second light-shielding element 12 is arranged between the plurality of first apertures 31 and the reference surface S. The second light-shielding element 12 has a plurality of second apertures 32 through which the light reflected from the document 6 passes. A portion of the second light-shielding element 12, excluding the second apertures 32, is a second light-shielding section 42 that blocks reflected light.A first translucent element 51 is arranged between the first light-shielding element 11 and the second light-shielding element 12.

[0014] The first light-blocking section 41 of the first light-blocking element 11 and the second light-blocking section 42 of the second light-blocking element 12 are light-blocking thin films formed from chromium oxide films applied to the first light-transmitting element 51. The first light-blocking element 11 is on a surface 51a (in Fig. 2 shown) of the first light-transmitting element 51, which faces the light-receiving pixels 10, and the second light-shielding element 12 is formed on a surface 51b (in Fig. 2) of the first translucent element 51, which faces the reference surface S. The first and second openings 31 and 32 are formed by etching using a deposited chromium oxide film as a mask pattern. Each of the first openings 31, for example, has a square shape of 48 µm × 48 µm, and each of the second openings 32, for example, has a square shape of 76 µm × 76 µm. The plurality of first openings 31 are arranged such that each corresponds to the plurality of light-receiving pixels 10. In the first embodiment, viewed in the Z-axis direction, the plurality of first openings 31 overlaps each of the plurality of light-receiving pixels 10. The plurality of second openings 32 are arranged such that each corresponds to the plurality of light-receiving pixels 10.In the first embodiment, viewed in the Z-axis direction, the plurality of second apertures 32 overlaps the plurality of light-receiving pixels 10. The plurality of first apertures 31 are arranged in two rows. The plurality of second apertures 32 are arranged in two rows. The first apertures 31 in each row are arranged in the X-axis direction. The second apertures 32 in each row are arranged in the X-axis direction. The plurality of first apertures 31 are arranged in an offset pattern. The plurality of second apertures 32 are arranged in an offset pattern.

[0015] The first translucent element 51 is an element that allows light to pass through it. The first translucent element 51 is, for example, a transparent glass plate. The first translucent element 51 does not have to be completely transparent, but can also be translucent. The first translucent element 51 has a refractive index n of, for example, 1.52. In the first embodiment, the first translucent element 51 consists of a single glass plate. The first translucent element 51 has a thickness t1 (in Fig. 3 shown) of, for example, 210 µm. The first translucent element 51 is at a distance t0 (in Fig. (3 shown) are arranged in the +Z-axis direction by the light-receiving pixels 10. The distance t0 between the light-receiving pixels 10 and the first light-transmitting element 51 is, for example, 250 µm. Part or all of the gap between the first openings 31 and the second openings 32 can be a space without a light-transmitting element.

[0016] In a case where wire bonding is used as a method for electrically connecting the imaging sensor chip 8 and the imaging sensor board 9, a wire could protrude from the surface of the imaging sensor chip 8 on the +Z-axis side by approximately 100 µm to 200 µm in the +Z-axis direction. Since, in the first embodiment, the distance t0 is 250 µm and thus longer than the wire, the wire protruding from the imaging sensor chip 8 does not obstruct the first light-transmitting element 51. In the first embodiment, a spacer element (not shown) with a thickness of 250 µm is arranged between the light-receiving pixels 10 and the first light-transmitting element 51 to precisely maintain the distance t0 of 250 µm.

[0017] The plurality of condenser lenses 14 are arranged between the plurality of second apertures 32 and the reference surface S. The optical axis of each of the condenser lenses 14 is designated by reference numeral 40. The condenser lenses 14 are arranged in one direction of the optical axis (i.e., the +Z-axis direction) at a distance from the plurality of second apertures 32. The condenser lenses 14 have the function of concentrating the light reflected onto the document 6. The condenser lenses 14 are, for example, convex lenses. The plurality of condenser lenses 14 are arranged such that each corresponds to the plurality of light-receiving pixels 10. In the first embodiment, viewed in the Z-axis direction, the plurality of condenser lenses 14 each overlap the plurality of light-receiving pixels 10. The plurality of condenser lenses 14 are arranged in two rows. The condenser lenses 14 in each row are arranged in the X-axis direction.The plurality of condenser lenses 14 are arranged in an offset pattern. The condenser lenses 14 arranged in the offset pattern form a condenser lens assembly 60. In the first embodiment, the diameter of each of the condenser lenses 14 is defined in the range of a few micrometers to a few millimeters. A radius of curvature of a surface of each condenser lens 14 is, for example, 0.35 mm. The condenser lens assembly 60 is a microlens assembly comprising the plurality of tiny condenser lenses 14. The plurality of condenser lenses 14 each overlap the plurality of first openings 31 and also each overlap the plurality of second openings 32.

[0018] The third light-blocking element 13 is arranged between the second light-blocking element 12 and the plurality of condenser lenses 14. The third light-blocking element 13 has the plurality of third apertures 33 through which light reflected from the document 6 passes. A section of the third light-blocking element 13, excluding the third apertures 33, is a third light-blocking section 43 that blocks reflected light. A second light-transmitting element 52 is arranged between the second apertures 32 and the third apertures 33.

[0019] The third light-shielding section 43 (in Fig. 3) of the third light-shielding element 13 is a light-shielding thin film formed from a chromium oxide film deposited on the second light-transmitting element 52. The third light-shielding element 13 is on a surface 52b (in Fig. 2) of the second translucent element 52, which faces the reference surface S. The third openings 33 are formed by etching using a deposited chromium oxide filament as a mask pattern. Fig. In the first embodiment, each of the third openings 33 is circular. The opening area of ​​each of the third openings 33 is larger than that of the first and second openings 31 and 32. That is, the diameter Φ of each of the third openings 33 is larger than each side of the first and second openings 31 and 32. The diameter is, for example, 170 µm. The plurality of third openings 33 are arranged such that each corresponds to the plurality of light-receiving pixels 10. In the first embodiment, viewed in the Z-axis direction, the plurality of third openings 33 overlap the plurality of light-receiving pixels 10. The plurality of third openings 33 are arranged in two rows. The third openings 33 in each row are arranged in the X-axis direction. The plurality of third openings 33 are arranged in an offset pattern.The plurality of third openings 33 each overlap the plurality of first openings 31 and also the plurality of second openings 32. In addition, the plurality of third openings 33 each overlap the plurality of condenser lenses 14.

[0020] The second translucent element 52 is an element that allows light to pass through it. The second translucent element 52 is, for example, a transparent glass plate. The second translucent element 52 does not have to be completely transparent, but can also be translucent. The second translucent element 52 has a refractive index n of, for example, 1.52. As in Fig. As shown in Figure 3, the second translucent element 52 has a thickness t2 that is greater than the thickness t1 of the first translucent element 51. For example, the thickness t2 of the second translucent element 52 is 700 µm. Part or all of the gap between the second openings 32 and the third openings 33 can be a space without a translucent element.

[0021] As in Fig. As shown in Figure 2, the second translucent element 52 is attached to the first translucent element 51 by bonding, for example with an adhesive, such that the center positions 93 of the third openings 33 overlap with the center positions 91 of the first openings 31 and the center positions 92 of the second openings 32. To increase the positioning accuracy when bonding the second translucent element 52 to the first translucent element 51, the surface 52a of the second translucent element 52 and the surface 51b of the first translucent element 51 can have alignment markings for positioning.

[0022] Fig. 5 is a diagram that shows a configuration of a Fig. Figure 1 schematically represents the optical illumination unit 2 shown and the illumination light emitted by the optical illumination unit 2. As shown in the Fig. 2 and Fig. As shown in Figure 5, the optical illumination unit 2 comprises a light source 20 and an optical fiber 21. The light source 20 is arranged at an end face 21a of the optical fiber 21. The light source 20 emits light 20a into the interior of the optical fiber 21. The light source 20 is, for example, a semiconductor light source. The semiconductor light source is, for example, a light-emitting diode (LED).

[0023] As in Fig. As shown in Figure 5, the light guide 21 causes light 20a emitted from the light source 20 to travel towards the document 6. The light guide 21 is, for example, a cylindrical element made of a translucent resin material. The light 20a emitted from the light source 20 spreads out within the light guide 21 by repeated total internal reflection. A scattering area 22 is formed on part of the inner surface of the light guide 21. The light 20a is scattered on the scattering area 22 and becomes scattered light. Part of the scattered light serves as illumination 25, which illuminates the document 6.

[0024] As in Fig. As shown in Figure 2, the illumination light 25 emitted onto document 6 is reflected on document 6 and becomes reflected light. The reflected light passes successively through the condenser lenses 14, the third apertures 33, the second transparent element 52, the second apertures 32, the first transparent element 51, and the first apertures 31 in that order.

[0025] Condition for acquiring a picture that is not affected by stray light

[0026] A condition for acquiring an image that is not affected by stray light in the image reading device 100 is now described. Fig. 6 is a diagram that shows part of the information in Fig. The configuration shown in Figure 3 and the reflected light passing through the second openings 32 and the first openings 31 are shown. Referring to Fig. Section 6 describes a condition for acquiring an image that is not affected by scattered light moving in the X-axis direction. Fig. The plurality of light-receiving pixels 10 arranged in the X-axis direction are also designated 10a, 10b, and 10c. Similarly, the plurality of first apertures 31 are also designated 31a, 31b, and 31c, and the plurality of second apertures 32 are also designated 32a, 32b, and 32c. In the first and second apertures 31 and 32, which overlap the light-receiving pixels 10, lines connecting the centers of the second apertures 32, the centers of the first apertures 31, and the light-receiving pixels 10 are also designated as optical axes 40a, 40b, and 40c.

[0027] In Fig. 6 is reflected light passing through the second openings 32 and the first openings 31, represented as light beams L1 to L3. As in Fig. As shown in Figure 6, the light beam L1 enters the light-receiving pixel 10a after passing through the second aperture 32a and the first aperture 31a. In other words, the light beam L1 entering the light-receiving pixel 10a is a light beam that has passed through the second aperture 32a and the first aperture 31a, which are located on the same optical axis 40a as that of the light-receiving pixel 10a. The light beam L2 is a light beam that passes through the second aperture 32b and the first aperture 31b, which are located on the optical axis 40b, which differs from the optical axis 40a. The light beam L3 is a light beam that passes through the first apertures 31c, which are located on the optical axis 40c, which differs from the optical axis 40a. The light beams L2 and L3 do not reach the light-receiving pixel 10a.In this case, the optical imaging unit 1 can obtain an image that is not affected by scattered light moving in the X-axis direction. In the first embodiment, the light beam that has passed through the second apertures 32 and the first apertures 31, which are located on the optical axis of the light-receiving pixels 10, enters the light-receiving pixels 10 on this optical axis. That is, the light-receiving pixels 10 and the first apertures 31 are in a one-to-one optical relationship, and the light-receiving pixels 10 and the second apertures 32 are in a one-to-one optical relationship.

[0028] Fig. 7A and Fig. Figure 7B shows diagrams describing a condition whereby reflected light, which has passed through the second apertures 32 and the first apertures 31 corresponding to the light-receiving pixels 10, enters the light-receiving pixels 10 in the image reading device 100. As in Fig. 7A and Fig. As shown in Figure 7B, the first transparent element 51 with refractive index n is located at a distance t0 from the light-receiving pixels 10. An air gap exists between the light-receiving pixels 10 and the first transparent element 51. If conditions 1 and 2 are met, reflected light that has passed through the second openings 32 and the first openings 31 corresponding to the light-receiving pixels 10 enters these light-receiving pixels 10. (Condition 1)

[0029] There are no light beams passing through the second apertures 32 and the first apertures 31, which have different optical axes. (Condition 2)

[0030] Light beams that have passed through the second apertures 32 and the first apertures 31, having the same optical axis, reach no other section than the light-receiving pixels 10 on this optical axis.

[0031] Conditions 1 and 2 are referred to in the Fig. 7A and Fig. 7B described. As in Fig. As shown in Figure 7A, condition 1 is met if the light beam satisfies a condition of total internal reflection. Specifically, a light-receiving pixel 10v, a plurality of light-receiving pixels 10, and light-receiving pixels 10u and 10w adjacent to the light-receiving pixel 10v are described. If the angle of incidence θ1 of a light beam L4 passing a point P3 in a first aperture 31v overlapping the light-receiving pixel 10v and a point P4 in a second aperture 32w overlapping the light-receiving aperture 32w is greater than a critical angle θ cThe light beam entering the first aperture 31v fulfills the condition of total internal reflection. Here, the angle of incidence θ1 of the light beam L4 is an angle formed by a normal N0 to the first light-shielding element 11 and the light beam L4. Point P3 is an end section of the first aperture 31v that is closest to the first aperture 31w. Point P4 is an end section of the second aperture 32w that is closest to the second aperture 32v.

[0032] A in Fig. The light beam L5 shown in Figure 7A passes through the second aperture 32w and enters a first aperture 31u. Since the light beam L4 is totally reflected in the first aperture 31v, the light beam L5, having a larger angle of incidence than that of the light beam L4, is totally reflected in the first aperture 31u. Therefore, the light beam L5 does not pass through the first aperture 31u.

[0033] Here, half the opening width, which is 1 / 2 the opening width of the first opening 31 in the X-axis direction, is defined as X1, and half the opening width, which is 1 / 2 the opening width of the second opening 32 in the X-axis direction, is defined as X2. A distance D1 in the X-axis direction between one end of the second opening 32w in the -X-axis direction and one end of the first opening 31v in the +X-axis direction is given by equation (1): D1=p−X1−X2

[0034] How Fig. 7A shows that, with respect to the angle of incidence θ1 of the light beam L4, equation (2) applies: tanθ1=D1 / t1=(p−X1−X2) / t1

[0035] In order for the light beam L4, which enters at the angle of incidence θ1, to satisfy the condition of total internal reflection, it is necessary that equation (3) is satisfied: n⋅sinθ1>1

[0036] From equation (2) and equation (3) the following equation (4) is derived with respect to the thickness t1 of the first translucent element 51 that satisfies condition 1: t1 <n2−1⋅(p−X1−X2)

[0037] In particular, if the thickness t1 of the first transparent element 51 is smaller than the value on the right-hand side of equation (4), the light beam L4 satisfies the condition of total internal reflection. In this case, condition 1 is met.

[0038] Next, condition 2 will be addressed with reference to Fig. 7B is described. A light-receiving pixel 10b from the plurality of light-receiving pixels 10 and light-receiving pixels 10a and 10c, which are adjacent to both sides of light-receiving pixel 10b in the X-axis direction, are described as an example. Condition 2 is met if a light beam L6, passing a point P5 in the second aperture 32b, which overlaps light-receiving pixel 10b, and a point P6 in the first aperture 31b, which overlaps light-receiving pixel 10b, reaches a region between light-receiving pixel 10a and light-receiving pixel 10c and does not enter either of light-receiving pixels 10a or 10c. The area between light-receiving pixel 10a and light-receiving pixel 10c is an area that lies between the right end of light-receiving pixel 10a and the left end of light-receiving pixel 10c, as shown in Fig. 7B shown.

[0039] The in Fig. The light beam L6 shown in Figure 7B is a light beam that passes through the second aperture 32b and the first aperture 31b, which overlaps the second aperture 32b. Fig. In 7B, the light beam L6 passes through an end section of the second aperture 32b, which is closest to the second aperture 32c, and then through an end section of the first aperture 31b, which is closest to the first aperture 31a. The light beam L6, having passed through the first aperture 31b, reaches a point Q0. Here, point Q0 represents a point located between the light-receiving pixel 10a and the light-receiving pixel 10c, which the light beam L6 reaches. Fig. 7B is point Q0, which is the point furthest away from light-receiving pixel 10b in the x-axis direction, that is, a point closest to light-receiving pixel 10a. In a case where the light beam L6 reaches a section of light-receiving pixel 10a that is closer to light-receiving pixel 10b than the end section of light-receiving pixel 10a that is closest to light-receiving pixel 10b, the light beam that has passed through the second aperture 32b and the first aperture 31b does not reach any light-receiving pixels (for example, light-receiving pixels 10a and 10c) except for light-receiving pixel 10b.

[0040] Assuming that the emission angle of the light beam L6 is α1 and the incidence angle of the light beam L6 is α2, the incidence angle α2 is obtained from equation (5): tanα2=(X1+X2) / t1

[0041] According to Snell's law, a relationship between the emission angle α1 and the incidence angle α2 is expressed by equation (6): n⋅sinα2=sinα1

[0042] The distance D2 from the optical axis 40b to the point Q0 is given by equation (7): D2=X1+t0⋅tanα1

[0043] Assuming that half the width of the light-receiving pixel 10b is 1 / 2 the width of the light-receiving pixel 10b in the X-axis direction X0, a condition that the point Q0 is closer to the light-receiving pixel 10b than an end section of the light-receiving pixel 10a in the +X-axis direction is expressed by equation (8): p−X0>X1+t0⋅tanα1

[0044] From equations (5) to (8) the following equation (9) is derived with respect to the thickness t1 of the first translucent element 51 that satisfies condition 2: t1>(X1+X2)⋅n2−1+n2⋅t02(p−X1−X0)2

[0045] That is, if the thickness t1 of the first translucent element 51 is greater than a value on the right-hand side of equation (9), then condition 2 described above is met.

[0046] In an example of the first embodiment, X0 = 31.5 µm, X1 = 24 µm, X2 = 38 µm, n = 1.52, t0 = 250 µm, and p = 252 µm. Substituting these values ​​into equation (4) and equation (9), the right-hand side of equation (4) is 217.5 µm and the right-hand side of equation (9) is 139 µm. Since, in this example, the thickness t1 of the first translucent element is 210 µm, equation (4), which defines the upper limit of the thickness t1, and equation (9), which defines the lower limit of the thickness t1, are satisfied. Accordingly, reflected light that has passed through the second apertures 32 and the first apertures 31, which correspond to the light-receiving pixels 10, enters the light-receiving pixels 10, so that an image that is not affected by stray light is acquired.

[0047] Next, further advantages achieved by the presence of the first and second light-shielding elements 11 and 12 in the image reading device 100 are described. As in Fig. As shown in Figure 7A, the light beam L4, which has passed through the second aperture 32w, is totally reflected in the first aperture 31v and therefore does not reach the light-receiving pixel 10v. The light beam L5 is also totally reflected in the first aperture 31u and therefore does not reach the light-receiving pixel 10u. Furthermore, as shown in Fig. Figure 7B shows that a light beam L7, which has passed through the second aperture 32c, is blocked by the first light-shielding section 41 of the first light-shielding element 11. Even if part of the light beam L7 is reflected at the first light-shielding element 11 and travels in the +Z-axis direction as a light beam L20, the light beam L20 is blocked by the second light-shielding section 42 of the second light-shielding element 12.

[0048] For comparison, a configuration is considered here as an image reading device in which a light-absorbing element with a through-hole extended in the +Z-axis direction between a light-receiving pixel and a reference surface is used instead of the one described in the Fig. 7A and Fig. The first and second light-shielding elements 11 and 12 and the first light-transmitting element 51 are shown in Figure 7B. In this configuration, a beam of light traveling parallel to the axis of the through-hole reaches the light-receiving pixel after passing through the through-hole. The inner surface of the through-hole acts as a light-shielding wall, blocking a beam of light with an angle of inclination relative to the axis. However, some of the light beam entering the through-hole may be scattered by the light-shielding wall. If, in this case, the scattered light beam enters a light-receiving pixel that does not correspond to the through-hole, the image information acquired by the light-receiving pixel will be affected by scattered light.On the other hand, in the first embodiment, since the light beam that has passed through the second openings 32 is totally reflected in the first openings 31 or by the first and second light-shielding elements 11 and 12, as in the . Fig. 7A and Fig. As shown in 7B, an image that is not affected by stray light is acquired, compared to a configuration in which the image reading device includes a light-absorbing element.

[0049] Subsequently, a condition is described that prevents a beam of light that has passed through the second apertures 32 and the first apertures 31 at points that overlap the light-receiving pixel 10 in one of two rows of the light-receiving pixel 10 from entering the light-receiving pixel 10 in the other row of the image reading device 100. Fig. 8 is a sectional view of the Fig. 1. Image reading device 100 shown along section line A8-A8. Specifically, Fig. Figure 8 is a section view of a plane containing point P1 and point P2, shown in Fig. 1, includes. In the following description, the items in the first row 8a (shown in Fig. 4) the light-receiving pixel 10 arranged, also referred to as a light-receiving pixel 10a, and the one in the second row 8b (shown in Fig. 4) The light-receiving pixel 10 arranged in the first and second apertures is also referred to as a light-receiving pixel 10e. The first and second apertures 31 and 32 that overlap the light-receiving pixel 10a are also referred to as 31a and 32a, and the first and second apertures 31 and 32 that overlap the light-receiving pixel 10e are also referred to as 31e and 32e. The condenser lens 14 that covers the second aperture 32a is also referred to as 14a, and the condenser lens 14 that overlaps the second aperture 32e is also referred to as 14e. The optical axis of the condenser lens 14a is referred to as 40a, and the optical axis of the condenser lens 14e is referred to as 40e.

[0050] Next, a condition is described that prevents a light beam that has passed through the second aperture 32e and the first aperture 31e from entering the light-receiving pixel 10a. This description, as in Fig. Figure 8 shows a backlight beam L8, which is an imaginary beam of light moving from the light-receiving pixel 10a to the first aperture 31e. The backlight beam L8 is a beam of light passing from a point R1 to a point R2 and reaching a point R3. Point R1 is an end of the light-receiving pixel 10a that is closest to the light-receiving pixel 10e. Point R2 is an end of the first aperture 31e that is closest to the first aperture 31a. Point R3 is a point located on an outer side of an end section of the second aperture 32e that is furthest from the second aperture 32a. If the backlight beam L8 reaches the first light-shielding section 41 or the second light-shielding section 42, a beam of light that has passed through the second aperture 32e and the first aperture 31e does not enter the light-receiving pixel 10a. Fig. 8 is described as an example of a case in which the backlight beam L8 reaches the second light-shielding section 42.

[0051] In Fig. In section 8, a distance between point R3 and the optical axis 40e is denoted by D3, and a length of 1 / 2 of a diagonal length of the square second aperture 32e is denoted by X. 20 This is defined as follows: If the distance D3 is greater than the length X 20 The backlight beam L8 reaches the second light-shielding section 42. Accordingly, the light beam that has passed through the second aperture 32e and the first aperture 31e does not enter the light-receiving pixel 10a. This is true even in a case where the distance D3 is smaller than the length X. 20 and the backlight beam L8 passes through the second opening 32e, the backlight beam L8 reaches the third light-shielding section 43 of the third light-shielding element 13, if the in Fig. The distance q shown in Figure 4 is large. Therefore, the light beam that has passed through the second aperture 32e and the first aperture 31e does not enter the light-receiving pixel 10a, even if the distance D3 is smaller than the length X. 20 , since the distance q is large and the image reading device 100 includes the third light-shielding element 13. Image recovery

[0052] The following describes a method for reconstructing an image of document 6 by the optical imaging unit 1 based on image information acquired by the light-receiving pixels 10. In the first embodiment, the center positions of the light-receiving pixels 10 in the first row 8a and the center positions of the light-receiving pixels 10 in the second row 8b are offset from each other in the Y-axis direction by a distance q, since the plurality of light-receiving pixels 10 are arranged in an offset pattern, as shown in Fig. 4 shown. Therefore, it is necessary to restore the image to a single image without positional shift, even in a case where document 6 is sampled in the Y-axis direction. In particular, it is sufficient to perform a process of shifting image information by the number of pixels corresponding to the distance q in the Y-axis direction after an image processing circuit (not shown) has acquired image information from the light-receiving pixels 10 in the first row 8a and image information from the light-receiving pixels 10 in the second row 8b. In Fig. In the first embodiment, the light-receiving pixels 10 in the second row 8b are shifted in the X-axis direction by a distance p / 2, which is 1 / 2 of the distance p, relative to the light-receiving pixels 10 in the first row 8a. The image processing circuit acquires outputs from the light-receiving pixels 10 at time intervals in which the document 6 is advanced in the Y-axis direction by a distance p / 2. In the first embodiment, the resolution in the X-axis direction is equal to the resolution in the Y-axis direction. The distance q, which indicates the amount of the positional shift of the image information, is preferably an integer multiple of the distance p / 2, but the present invention is not limited to this example. The image processing circuit can determine a luminance value at a sub-pixel position using a pixel interpolation process to synthesize image information using the determined luminance value.The image processing circuit can synthesize the acquired image information by shifting a time point at which the light-receiving pixels 10 in the first row 8a acquire image information and a time point at which the light-receiving pixels 10 in the second row 8b acquire image information, which are shifted relative to each other. Increased depth of field

[0053] In comparison to the first and second examples, a configuration is now described in which the depth of field of the image reading device is increased by 100. The following description refers to an example of a configuration where the depth of field is increased to acquire an image with a resolution of 200 dpi (i.e., distance p = 252 µm).

[0054] Fig. Figure 9 is a diagram that schematically represents reflected light entering the light-receiving pixel 10b in an image reading device 100a according to a first comparative example. As in Fig. As shown in Figure 9, the image reading device 100a of the first comparative example differs from the image reading device 100 according to the first embodiment (shown in Figure 9). Fig. 15 (which will be described later) by the fact that it does not include any of the third light-shielding element 13, the condenser lenses 14, and the second light-transmitting element 52 in the first embodiment. The light beams L11 to L14 are represented as light beams entering the light-receiving pixel 10b. In the following description, a group of a plurality of light beams is referred to as a light flux. Light beam L11 is a light beam entering an end section of the light-receiving pixel 10b in the X-axis direction, and light beam L12 is a light beam entering the other end section of the light-receiving pixel 10b in the X-axis direction. Light beam L13 is a light beam entering a section near the center of the light-receiving pixel 10b, and light beam L14 is another light beam entering a section near the center of the light-receiving pixel 10b.The distance between the light beams L11 and L12 in the X-axis direction and the distance between the light beams L13 and L14 in the X-axis direction each increase when the distance to the second opening 32b in the +Z-axis direction increases.

[0055] Fig. Figure 10 is a diagram showing imaginary backlight beams 61b to 63b, moving from the light-receiving pixel 10b in the +Z-axis direction, in the image reading device 100a according to the first comparison example. The backlight beams 61b to 63b are backlight beams moving in the +Z-axis direction from an object surface that is a light-receiving surface of the light-receiving pixel 10b. Backlight beam 61b is a backlight beam moving in the +Z-axis direction from a point on the object surface that has an object height h = 0. Backlight beam 62b is a backlight beam moving in the +Z-axis direction from a point on the object surface that has an object height h = X0 / 2. The backlight 63b is a backlight beam that moves in the +Z-axis direction from a point on the object surface that has an object height h = X0. Fig. 10 and those described later Fig. 13, Fig. 16 and Fig. 20 the first transparent element 51, having refractive index n and thickness t1, is replaced by a first transparent element 51 with a refractive index 1 and a thickness t1 / n.

[0056] Fig. 11 is a diagram showing the spread of the in Fig. The depicted backlight beams 61b to 63b are shown in 10. Fig. 11 is the one in Fig. The optical imaging unit 101a shown in Figure 10 is reduced in size to emphasize the scattering of the backlight beams 61b to 63b. Fig. Targets 71 to 73 are arranged at a distance (for example, 2 mm) from the optical imaging unit 101a in the +Z-axis direction. In a case where all backlight beams pass through targets 71 to 73, a sufficiently large depth of field is obtained. Here, in the case of acquiring an image with a resolution of 200 dpi, as a guideline, a resolution of 200 dpi is obtained if a light beam from an area of ​​two pixels or less on a document reaches a light-receiving pixel in the optical imaging unit. The reason why sufficient resolution is achieved even with a dispersion of two pixels is that a light flux on the optical axis reaches the light-receiving pixel with minimal loss, and the proportion of light flux coming from the field edges of the two pixels on the document and reaching the light-receiving pixel is small. Fig. 11 Each width of targets 71 to 73 in the X-axis direction corresponds to a size of two pixels. Since, in the example of the first embodiment, the distance p in the X-axis direction between adjacent light-receiving pixels 10 is 252 µm, the width of targets 71 to 73 in the X-axis direction is 252 µm.

[0057] In Fig. 11 is a position where the scattering of the light flux of the backlight beams 61b to 63b occurs at two pixels on document 6 (in Fig. 1) corresponds to position 70. In the following description, in each of the image reading devices according to the first and second comparative examples and the first embodiment, a distance from the optical imaging unit to position 70 is designated by L. zThe document support table must be arranged on the +Z-axis side of the optical imaging unit in the image reading device. As in the first embodiment, the optical illumination unit is, in some cases, arranged between the optical imaging unit and the document support table. The depth of field necessary to acquire an image with a resolution of 200 dpi is thus determined by a distance from the document support table (the upper glass plate 7 in Fig. 9) shown at position 70. In the following description, the depth of field of the image reading devices according to the first and second comparative examples and the first embodiment is referred to as DOF.

[0058] As in the Fig. 10 and Fig. As shown in Figure 11, in the first comparative example, the backlight beams 61b to 63b spread continuously in the X-axis direction even after passing through the second aperture 32b, so that position 70 is close to the optical imaging unit 101a and the distance L z is small. In the first comparative example, the distance L is z For example, about 0.5 mm. So, if, as in Fig. 9 shows the upper glass plate 7, having essentially the same thickness as the distance L z Since the optical illumination unit 2 is positioned between the second aperture 32b and the reference surface S, the depth of field (DOF) in the first comparison example may not be sufficiently large. In the first comparison example, it is difficult to position the optical illumination unit 2 between the optical imaging unit 101a and the upper glass plate 7.

[0059] Fig. Figure 12 is a diagram schematically illustrating the entry of reflected light into the light-receiving pixel 10b in an image reading device 100b according to a second comparative example. The second comparative example differs from the image reading device 100 according to the first embodiment (shown in Figure 12). Fig. 15, which is described later) in that the first embodiment does not include either the third light-blocking element 13 or the second light-transmitting element 52. The second comparative example also differs from the image reading device 100 according to the first embodiment in the arrangement of the condenser lenses 14 on the second light-blocking element 12.

[0060] Fig. Figure 13 is a diagram showing imaginary backlight beams 61b to 63b moving from the light-receiving pixel 10b in the +Z-axis direction in the image reading device 100b according to the second comparison example. In the second comparison example, the focal length of the condenser lens 14b is adjusted such that a point on the light-receiving pixel 10b is focused on the target 73 in the targets 71 to 73 that are furthest from the optical imaging unit 101b in the +Z-axis direction. Here, the distance from the light-receiving pixel 10b to the condenser lens 14b is expressed by t0 + t1 / n.

[0061] For example, if in the second comparison example t0 = 0.25 mm, t1 = 0.21 mm, and n = 1.52, the distance from the light-receiving pixel 10b to the condenser lens 14b is 0.39 mm. In a case where the targets 71 to 73 are arranged at a distance of 2.0 mm from the optical imaging unit 101b, the distance from the optical imaging unit 101b to the target 73 is 6.0 mm. Thus, the distance from the light-receiving pixel 10b to the condenser lens 14b is significantly less than the distance from the optical imaging unit 101b to the target 73. The focal length of the condenser lens 14b is therefore approximately 0.39 mm. At this time, as in Fig. Figure 13 shows backlight beams that form the light flux of backlight beam 61b, which has passed through the condenser lens 14b, moving parallel to each other. Backlight beams that form the light flux of backlight beam 62b also move parallel after passing through the condenser lens 14b, and backlight beams that form the light flux of backlight 63b also move parallel after passing through the condenser lens 14b. The expression "move parallel" here includes "move essentially parallel".

[0062] Fig. 14 is a diagram showing the spread of the in Fig. The 13 depicted backlight beams 61b to 63b are shown. Fig. 14 is the one in Fig. The optical imaging unit 101b shown in Figure 13 is reduced in size to emphasize the spread of the backlights 61b to 63b. As shown in the Fig. 13 and Fig. As shown in Figure 14, in the second comparative example, the luminous flux of the backlight beam 61b, the luminous flux of the backlight beam 62b, and the luminous flux of the backlight 63b are focused by the condenser lens 14b. Accordingly, position 70 moves away in the +Z-axis direction, and the distance L z is larger than in the first comparison example. In the second comparison example, the distance L is z For example, approximately 1.0 mm. As in Fig. As shown in Figure 12, however, the depth of field DOF is also not sufficiently large in the second comparative example if the upper glass plate 7 and the optical illumination unit 2 are arranged between the condenser lenses 14 and the reference surface S.

[0063] Fig. Figure 15 is a diagram schematically representing reflected light entering the light-receiving pixel 10b in the image reading device 100 according to the first embodiment. As in Fig. As shown in Figure 15, in the image reading device 100 the condenser lenses 14 are arranged in the +Z-axis direction at a distance from the second light-shielding element 12. In particular, the condenser lenses 14 are arranged at a sufficient distance from the second light-shielding element 12, with the second light-transmitting element 52 and the third light-shielding element 13 located between them.

[0064] Fig. Figure 16 is a diagram showing imaginary backlight beams 61b to 63b moving from the light-receiving pixel 10b in the +Z-axis direction in the image reading device 100a according to the first comparison example. Fig. 16 and Fig. In section 20, which will be described later, the second transparent element 52 with refractive index n and thickness t2 is replaced by a second transparent element 52 with a refractive index 1 and a thickness t2 / n to simplify the description. As in Fig. As shown in Figure 16, the condenser lens 14 is arranged at a distance t2 / n from the second light-shielding element 12.

[0065] Fig. 17 is a diagram showing the spread of the in Fig. The depicted backlight beams 61b to 63b are shown in 16. Fig. 17 is the one in Fig. The optical imaging unit 1 shown in Figure 16 is reduced in size to emphasize the spread of the backlights 61b to 63b. In the image reading device 100, the focal length of the condenser lens 14b is adjusted so that a point on the light-receiving pixel 10b is focused at a point located between the target 71 and the target 72 (for example, a point 3.0 mm away from the optical imaging unit 1 in the +Z-axis direction). As shown in the Fig. 16 and Fig. As shown in Figure 17, the principal light beams of the backlight beams 61b to 63b, which have passed through the condenser lens 14b, are essentially parallel in the +Z-axis direction. Here, the principal light beams are the light beams that pass through the center of the light beam. Furthermore, as shown in Fig. 17 shown, in the image reading device 100 the distance L z in the first embodiment greater than the distance L z In the second comparison example, position 70 is further away in the +Z-axis direction than position 70 in the second comparison example. In the image reading device 100, the distance L is zFor example, approximately 3.5 mm. Accordingly, a sufficiently large depth of field (DOF) can be achieved in the image reading device 100, even if the upper glass plate 7 and the optical illumination unit 2 are positioned between the second aperture 32b and the reference surface S. For example, if a space of 1.5 mm is required to position the upper glass plate 7 and the optical illumination unit 2, a depth of field (DOF) of 2.0 mm can be achieved.

[0066] Thus, in the image reading device 100 according to the first embodiment, the condenser lens 14b is arranged at a distance from the second apertures 32, such that the depth of field (DOF) of the image reading device 100 is greater than the depth of field (DOF) in the first and second comparative examples. In the image reading device 100, even if half the width X0 of the light-receiving pixels 10, half the aperture width X1 of the first apertures 31, and half the aperture width X2 of the second apertures 32 are increased, the depth of field (DOF) can be increased by increasing the amount of light received by the light-receiving pixels 10, since the depth of field (DOF) can be increased. Lower limit of the thickness of the second translucent element

[0067] The following describes a lower limit for the thickness t2 of the second translucent element 52, which is necessary for increasing the depth of field DOF. Fig. Figure 18 is a diagram showing imaginary backlight beams 61b and 63b from the light-receiving pixel 10b in the +Z-axis direction in the image reading device 100 in a case where one of the first and second apertures 31 or 32 is an aperture stop. The reference numeral 30 in Fig. 18 designates the aperture diaphragm of the optical imaging unit 1. In other words, the aperture diaphragm 30 is one of the first and second apertures 31, 32. Fig. 18. A distance from the light-receiving pixel 10b to the aperture 30 is designated L0, and a distance from the aperture 30 to the third opening 33b is designated L1.

[0068] If the first opening 31 is the aperture 30, the distance L0 and the distance L1 are expressed by equation (10) and equation (11): L0=t0 L1=t1 / n+t2 / n

[0069] If the second opening 32 is the aperture diaphragm 30, the distance L0 and the distance L1 are expressed by equation (12) and equation (13): L0=t0+t1 / n L1=t2 / n

[0070] In Fig. In Figure 18, a backlight beam passing the center of the aperture diaphragm 30 within the backlight beam 61b, which travels from the center of the light-receiving pixel 10b to the aperture diaphragm 30, is represented as a principal beam 64b. A backlight beam passing the center of the aperture diaphragm 30, within the backlight beam 63b, and traveling from an end section of the light-receiving pixel 10b in the +X-axis direction to the aperture diaphragm 30, is represented as a principal beam 65b. If the principal beam 64b and the principal beam 65b are parallel on the +Z-axis side of the condenser lenses 14, the backlight beams 61b and 63b are combined. The optical system in which the principal beam 64b and the principal beam 65b are parallel is called a telecentric optical system. To achieve the telecentric optical system, it is necessary that the focal length f of the condenser lens 14b matches the distance L1.That is, the telecentric optical system is achieved if the following equation (14) is satisfied: f=L1

[0071] In Fig. 18 is a plane containing a point where the backlight beams 61b and 63b are collected and which lies parallel to the XY plane, denoted by 80, and the distance from the condenser lens 14b to the plane 80 is denoted by L2. Fig. 18 is the distance from the optical imaging unit 1 (i.e., the condenser lens 14b) to the target 74 with L z The area in which target 74 is illuminated by a light flux is essentially equal to the aperture width of the third aperture 33 in the X-axis direction. The aperture width of the third aperture 33 corresponds to a size of two pixels. Target 74 is located at a distance L2 from plane 80 in the +Z-axis direction. To increase the depth of field (DOF), the distance L must be increased. zThe distance L2 increases. As the distance L increases, the distance L also increases. z . From the lens formula, the following equation (15) results: 1 / (L0+L1)+1 / L2=1 / f

[0072] From equation (14) and equation (15) the following equation (16) is derived with respect to the distance L2: L2=L1⋅(L0+L1) / L0

[0073] Equation (16) shows that as the distance L1 increases, the distance L2 also increases. To increase the distance L1, it is necessary to increase the thickness t2 of the second translucent element 52 (in Fig. 3 shown) to increase.

[0074] In this context, the lower limit of the thickness t2 of the second translucent element 52 is taken into account. First, to increase the depth of field DOF, the distance L2 must be greater than the sum of the distance L0 and the distance L1, as expressed in equation (17): L2>L0+L1

[0075] The sum of the distance L0 and the distance L1 is obtained from equations (10) and (11) or equations (12) and (13) by equation (18): L0+L1=t0+(t1 / n)+(t2 / n)

[0076] Since in the example of the first embodiment t0 = 0.25 mm, t1 = 0.21 mm, t2 = 0.70 mm and n = 1.52, if these values ​​are substituted into equation (18), the sum of the distance L0 and the distance L1 is 0.85 mm. Therefore, to increase the depth of field (DOF), the distance L2 must be greater than 0.85 mm.

[0077] In Fig. 18 is the distance L z approximately twice the distance L2. Since the lower limit of the distance L2 is, for example, 0.85 mm, the lower limit of the distance L is z In the example of the first embodiment, 1.7 mm. To increase the depth of field (DOF), the distance L must be increased. z for example, 1.7 mm or more.

[0078] Referring to a relationship between the distance L1 and the distance L0, the following equation (19) is derived from equation (16) and equation (17): L1>L0

[0079] In the case where the first opening 31 is the aperture diaphragm 30, if equation (10) and equation (11) are substituted into equation (19), equation (20) is derived with respect to the thickness t2 of the second transparent element 52: t2>n⋅t0−t1

[0080] In the case where the second opening 32 is the aperture diaphragm 30, if equation (12) and equation (13) are substituted into equation (19), equation (21) is derived with respect to the thickness t2 of the second translucent element 52: t2>n⋅t0+t1

[0081] If the thickness t2 of the second transparent element 52 satisfies equation (21), then the thickness t2 also satisfies equation (20), and thus the lower limit of the thickness t2 of the second transparent element 52, which is necessary to increase the depth of field (DOF), is n · t0 - t1, expressed by equation (20). Therefore, if the thickness t2 of the second transparent element 52 satisfies equation (20), a sufficiently large depth of field (DOF) can be obtained. Upper limit of thickness of second translucent element

[0082] The upper limit of the thickness t2 of the second translucent element 52 is now described in comparison to a comparative example. Fig. Figure 19 is a diagram showing an imaginary backlight beam 81b, moving from the light-receiving pixel 10b in the +Z-axis direction, in an image reading device 100c according to a third comparative example. The backlight beam 81b is backlight that, from an end section of the light-receiving pixel 10b in the +X-axis direction, passes through a section of the aperture diaphragm 30b near an end of the aperture diaphragm 30b in the -X-axis direction and passes through the third aperture 33a.

[0083] The distance L1 from the aperture diaphragm 30b to the third opening 33b is greater in the third comparative example than the distance L1 in the Fig. Figure 18 shows the image reading device 100. Thus, the backlight beam 81b does not pass through the third aperture 33b, which is located at a different position than the light-receiving pixel 10b, but rather through the third aperture 33a, which is located at a position that does not overlap the light-receiving pixel 10b. The backlight beam 81b becomes the backlight beam 82b after passing through the third aperture 33a and the condenser lens 14a. The distance between the backlight beam 82b and the optical axis 40b in the X-axis direction increases with distance from the condenser lens 14a in the +Z-axis direction. This means that, in the third comparative example, an excessively large distance L1 causes the presence of light beams that pass through the third apertures, with the exception of the third aperture 33b, at a different position than the light-receiving pixel 10b, and the optical imaging unit 1 acquires an image impaired by stray light.The following description refers to the upper limit of the distance L1, which is necessary to prevent the backlight beam 81b from passing through the third aperture 33a adjacent to the third aperture 33b, which overlaps the light-receiving pixel 10b, and to the upper limit of the thickness t2 of the second light-transmitting element 52.

[0084] Next, in Fig. 19. A half-opening width, which is 1 / 2 the opening width of each of the third openings 33a and 33b in the X-axis direction, is denoted by X3. Since the distance between the center positions of the adjacent third openings 33a and 33b in the X-axis direction is p, the half-opening width X3 is less than 1 / 2 the distance p. Thus, the relationship between the half-opening width X3 and the distance p is expressed by equation (22): X3 <p / 2

[0085] Half an opening width, which is half the width of opening 30b in the X-axis direction, is designated X4. If the first opening 31 (in Fig. (1 shown) is the aperture diaphragm 30b, so half the aperture width X4 is expressed by equation (23): X4=X1

[0086] If the second opening is 32 (in Fig. If the aperture 30b is shown in Figure 1, then half the aperture width X4 is expressed by equation (24): X4=X2

[0087] In Fig. In Equation 19, an angle formed by the backlight beam 81b with respect to the optical axis 40b is denoted by θ2. In a case where the backlight beam 81b moves from an end section of the light-receiving pixel 10b in the +X-axis direction to an end section of the aperture diaphragm 30b in the -X-axis direction, the angle θ2 is expressed by equation (25): tanθ2=(X0+X4) / L0

[0088] Assuming that the distance between point R4 in the third aperture 33a, which the backlight beam 81b reaches, and the optical axis 40b is A, the angle θ2 formed by the backlight beam 81b with respect to the optical axis 40b is expressed by equation (26) described below, which differs from equation (25). tanθ2=(X0+A) / (L0+L1)

[0089] From equation (26) and equation (27), equation (27) is derived with respect to the distance A: A=((L0+L1)⋅(X0+X4) / L0)−X0

[0090] A condition that prevents the backlight beam 81b from passing through the third opening 33a is expressed by equation (28): A <p−X3

[0091] Equation (29) regarding the upper limit of the distance L1 is derived from equation (27) and equation (28). L1 <L0⋅(p−X3−X4) / (X0+X4)

[0092] Therefore, if the distance L1 satisfies equation (29), the backlight beam 81b does not pass through the third aperture 33a adjacent to the third aperture 33b, which overlaps the light-receiving pixel 10b. Next, the upper limit of the thickness t2 of the second light-transmitting element 52 is obtained from equation (29).

[0093] If the first opening 31 is the aperture diaphragm 30, equation (30) regarding the thickness t2 of the second transparent element 52 is derived from equations (10), (11) and (23) and equation (29): t2<(n⋅t0⋅(p−X3−X1) / (X0+X1))−t1

[0094] Next, if the second opening 32 is the aperture diaphragm 30, equation (31) regarding the thickness t2 of the second translucent element is derived from equations (12), (13) and (24) and equation (29): t2<(n⋅t0+t1)⋅(p−X3−X2) / (X0+X2)

[0095] Fig. Figure 20 is a diagram showing an imaginary backlight beam 81b moving from the light-receiving pixel 10b in the +Z-axis direction in the image reading device 100 according to the first embodiment in the case where the first opening 31b is the aperture diaphragm 30b (in Fig. 19 shown). As in Fig. As shown in Figure 20, the backlight beam 81b, which travels from an end section of the light-receiving pixel 10b in the +X-axis direction to the first aperture 31b, passes through the second aperture 32b. The backlight beam 81b, having passed through the second aperture 32b, reaches the third light-shielding element 13. Assuming that a line extending from a point where the backlight beam 81b reaches the third light-shielding element 13 to an imaginary line V, is a line 83b, with line 83b intersecting the imaginary line V at point Q1. The imaginary line V is a line passing through an end section of the third aperture 33a in the +X-axis direction and parallel to the optical axes 40a and 40b.A point where a line 84b, connecting an end section of the light-receiving pixel 10b in the +X-axis direction and an end section of the second aperture 32b in the -X-axis direction, intersects the imaginary line V is designated Q2. The line 84b does not pass through the first aperture 31b, and thus a beam of light moving along the line 84b is blocked by the first light-shielding element 11.

[0096] The distance from point Q1 to the second light-blocking element 12 corresponds to a value obtained by dividing the right-hand side of equation (30) by the refractive index n of the second light-transmitting element 52 (i.e., M1 / n). The distance from point Q2 to the second light-blocking element 12 corresponds to a value obtained by dividing the right-hand side of equation (31) by the refractive index n (i.e., M2 / n).

[0097] Here, M1 and M2 are expressed individually by equation (32) and equation (33): M1=(n⋅t0⋅(p−X3−X1) / (X0+X1))−t1 t2<(n⋅t0+t1)⋅(p−X3−X1) / (X0+X2)

[0098] If the first opening 31 is the aperture diaphragm 30, then M1 ≥ M2. Fig. According to equations (30) and (32), the thickness t2 of the second light-transmitting element 52 is smaller than M1, since the first aperture 31 is the aperture diaphragm 30. Accordingly, no backlight passes through the third aperture 33a at a position that does not overlap the light-receiving pixel 10b, and an image unaffected by stray light can be acquired. Fig. In 20, the thickness t2 of the second transparent element 52 is greater than M2, since point Q2 is located on the side of the -Z-axis of the third aperture 33a. However, as described above, a beam of light traveling along line 84b is blocked by the first light-shielding element 11. Accordingly, if the first aperture 31 is the aperture diaphragm 30, the relationship between the thickness t2 of the second transparent element 52 and M2 is disregarded, and it is necessary to satisfy the condition that the thickness t2 of the second transparent element 52 is less than M1.

[0099] If the second aperture 32 is the aperture 30, then M2 ≥ M1. In this case, if the thickness t2 of the second transparent element 52 is less than M2, no backlight passes through the third aperture 33a at a position that does not overlap the light-receiving pixel 10b. As described above, the upper limit of the thickness t2 of the second transparent element 52 required to prevent backlight from passing through the third aperture 33a is obtained from equation (34): t2 <MAX{M1,M2}

[0100] Since in the example of the first embodiment t0 = 250 µm, t1 = 210 µm, n = 1.52, X0 = 35.0 µm, X1 = 27.0 µm, X2 = 43.0 µm and X3 = 85.0 µm, if these values ​​are substituted into equation (32) and equation (33), M1 = 769 µm and M2 = 1095 µm are obtained. From equation (34) the upper limit of the thickness t2 of the second translucent element is thus 1095 µm. Since in the example of the first embodiment the thickness t2 of the second translucent element is 700 µm, equation (34) is satisfied.

[0101] As described above, to increase the depth of field, the focal length f of the condenser lenses 14 must match the distance L1. However, as described above, the value of the distance L1 varies depending on which of the first apertures 31 or the second apertures 32 is the aperture diaphragm 30. Therefore, the focal length f of the condenser lenses 14 must satisfy the condition represented by equation (35): t2 / n≤f≤(t1 / n)+t2 / n

[0102] Even if equation (35) is satisfied, the scattering of backlight is large in some cases. Therefore, it is necessary to determine the position of a preferred focal point F of the condenser lens 14 in order to reduce backlight scattering. Focal point position of condenser lens

[0103] A position of the focal point F of the condenser lens 14, which is necessary to reduce the scattering of backlight, is now described using a tracking result of backlight. Fig. Figure 21A is a diagram showing imaginary backlight beams moving from the light-receiving pixel 10b in the +Z-axis direction in an image reading device 100d according to a fourth comparison example. In the fourth comparison example, the position of the focal point F of the condenser lens 14b in the +Z-axis direction overlaps with the position of the light-receiving pixel 10b in the +Z-axis direction. As in Fig. As shown in 21A, in the fourth comparative example the distance L z from the condenser lenses 14 to the plane 80 is small, and the depth of field is small.

[0104] Fig. Figure 21B is a diagram showing imaginary backlight beams moving from the light-receiving pixel 10b in the +Z-axis direction in an image reading device 100e according to a fifth comparative example. In the fifth comparative example, the position of a focal point F of the condenser lens 14b in the +Z-axis direction overlaps with the position of the second aperture 32b in the +Z-axis direction. In the fifth comparative example, the focusing force of the condenser lens 14b is high, and the position at which backlight is focused is close to the condenser lens 14b. Accordingly, in the fifth comparative example, the scattering of backlight that has passed through the plane 80 is large, and thus the distance L z small, and as in the fourth comparison example, the depth of field is small.

[0105] Fig. Figure 22A is a diagram showing the imaginary backlight moving from the light-receiving pixel 10b in the +Z-axis direction in the image reading device 100 according to the first embodiment. In the image reading device 100, the position of the focal length F of the condenser lens 14b in the +Z-axis direction is located between the light-receiving pixel 10b and the first aperture 31b. Fig. Figure 22B is a diagram showing imaginary backlighting moving from the light-receiving pixel 10b in the +Z-axis direction in an image reading device 110 according to a variant of the first embodiment. In the image reading device 110, the position of the focal point F of the condenser lens 14b in the +Z-axis direction overlaps with the position of the first aperture 31b in the +Z-axis direction.

[0106] The in Fig. 22B shown value of distance L z is essentially the same as in Fig. 22A shown value of the distance L zIn image reading devices 100 and 110, the distances L are different compared to the fourth and fifth comparison examples. z large, and the depth of field can be increased.

[0107] Out of Fig. 21A and Fig. 21B and Fig. 22A and Fig. Figure 22B shows that if the position of the focal point F of the condenser lens 14b is set between the light-receiving pixel 10b corresponding to the condenser lens 14b and the second aperture 32b corresponding to the light-receiving pixel 10b, backlight scattering can be reduced and the depth of field of the image reading device 100 can be increased. A region between the light-receiving pixel 10b and the second aperture 32b is a region that lies between the surface of the second light-shielding element 12 in the -Z-axis direction and the surface of the light-receiving pixel 10 in the +Z-axis direction, as shown in Figure 22B. Fig. 2 shown. Third light-blocking element

[0108] The following refers to the Fig. 1, Fig. 2, Fig. 3 and Fig. 16 the third light-shielding element 13 of the image reading device 100 according to the first embodiment described. As in Fig. As shown in Figure 1, the third light-shielding element 13 comprises circular third apertures 33. The aperture width (i.e., the diameter) of each of the third apertures 33 is smaller than the effective diameter of each of the condenser lenses 14. Thus, a Fig. The backlight beam 66b shown in Figure 16 is the third light-shielding element 13. This means that since the image reading device 100 contains the third light-shielding element 13, stray light generated on the document 6 is blocked by the third light-shielding element 13, and thus stray light does not reach the light-receiving pixel 10b. Accordingly, the image reading device 100 prevents deterioration of the image's contrast or the generation of a ghost image, and thus the image reading device 100 is able to read an image with high quality.

[0109] The diameter Φ of the in Fig. The third opening 33b shown in Figure 16 is larger than the width of the light flux from each of the rear light beams 61b to 63b in the X-axis direction. Accordingly, all back light beams 61b to 63b pass through the third opening 33b. As shown in the Fig. 2 and Fig. As shown in Figure 3, in the configuration in which the third light-shielding element 13, comprising the third apertures 33 and the condenser lenses 14, is arranged between the second apertures 32 and the reference surface S, the reduction in the amount of light received by the light-receiving pixels 10 is therefore small. Advantages of the first embodiment

[0110] As described above, in the image reading device 100 according to the first embodiment, the condenser lenses 14 are arranged at a distance from the second apertures 32. Thus, even if the width of the light-receiving pixels 10 in the X-axis direction and the aperture areas of the first and second apertures 31 and 32 are increased to increase the amount of light received by the light-receiving pixels 10, the depth of field can be increased.

[0111] Since the focal point F of the condenser lens 14 in the image reading device 100 according to the first embodiment lies between the light-receiving pixels 10 and the second apertures 32, the depth of field can be further increased.

[0112] In the image reading device 100 according to the first embodiment, the thickness t2 of the second light-transmitting element 52 satisfies equation (20), so that the depth of field can be further increased.

[0113] In the image reading device 100 according to the first embodiment, the thickness t1 of the first light-transmitting element 51 satisfies equation (4), reflected light beams that have passed through the second openings 32 and the first openings 31, which correspond to the light-receiving pixels 10, enter the light-receiving pixels 10, and thus an image that is not affected by scattered light can be acquired.

[0114] In the image reading device 100 according to the first embodiment, the thickness t1 of the first light-transmitting element 51 satisfies equation (9), so that reflected light beams that have passed through the second openings 32 and the first openings 31 corresponding to the light-receiving pixels 10 enter the light-receiving pixels 10, and thus an image that is not affected by scattered light can be acquired.

[0115] Furthermore, in the image reading device 100 according to the first embodiment, the thickness t2 of the second light-transmitting element 52 satisfies equation (34), so that reflected light beams that have passed through the third aperture, second apertures 32 and the first apertures 31 corresponding to the light-receiving pixels 10 enter the light-receiving pixels 10, and thus an image that is not affected by stray light can be acquired. Variant of first embodiment

[0116] Fig. Figure 23 is a diagram showing imaginary backlight beams L15 to L18, which move from the light-receiving pixel 10b in the +Z-axis direction, in an image reading device 120 according to a variant of the first embodiment. The image reading device 120 differs from the image reading device 100 in the arrangement positions of the condenser lenses 14a to 14c. In particular, in the image reading device 120, the center positions 94 of the condenser lenses 14a to 14c are displaced in the +X-axis direction relative to the center positions 90 of the light-receiving pixels 10a to 10c. As in Fig. As shown in Figure 23, in the image reading device 120, the backlight beams L15 to L17 pass through the condenser lens 14b and are then tilted in the +X-axis direction. This tilting, however, does not affect image performance such as resolution. The backlight beam L18 is a backlight that travels from an end section of the light-receiving pixel 10b in the +X-axis direction to the third light-shielding element 13 through the second aperture 32b. The backlight beam L18 comprises a backlight beam L18a, which is blocked by the third light-shielding element 13, and a backlight beam L18b, which passes through the condenser lens 14a, assuming that the image reading device 120 does not contain the third light-shielding element 13. The backlight beam L18b travels in a different direction than the backlight beams L15 to L17 (i.e., in a direction tilted in the -X-axis direction).

[0117] In Fig. 23, since the image reading device 120 contains the third light-shielding element 13, the backlight beam L18a is blocked by the third light-shielding section 43. Here, a difference between the diameter of the third apertures 33a to 33c and the effective diameter of the condenser lenses 14a to 14c is a permissible error in the arrangement positions of the condenser lenses 14a to 14c. In the image reading device 120, the diameter of the third apertures 33a to 33c is smaller than the effective diameter of the condenser lenses 14a to 14c. Thus, even if the arrangement positions of the condenser lenses 14a to 14c are shifted relative to the light-receiving pixels 10a to 10c, an image unaffected by stray light can be acquired.

[0118] Fig. Figure 24 is a perspective view showing an optical imaging unit 1a of the image reading device 130 according to the variant of the first embodiment of the present invention. Fig. Figure 25 is a diagram showing the entry of reflected light into the light-receiving pixels 10 in the Fig. The image reading device shown in section 24 is schematically represented in section 130. The same reference symbols are used as in the Fig. 1 denotes the same or corresponding components as those in Fig. The image reading device 130 is shown in Figure 1, and a description thereof is omitted. The image reading device 130 differs from the image reading device 100 according to the first embodiment by the arrangement positions of the condenser lenses 14.

[0119] As in the Fig. 24 and Fig. As shown in Figure 25, in the image reading device 130, the third translucent element 53 is arranged between the second translucent element 52 and the condenser lenses 14. The third translucent element 53 is, for example, a transparent glass element. The third translucent element 53 does not have to be completely transparent, but can also be translucent.

[0120] The third translucent element 53 is attached to the third light-blocking element 13 by bonding, for example with an adhesive. The condenser lenses 14 are arranged on the third translucent element 53. The condenser lenses 14 are formed on a surface 53a of the third translucent element 53 facing the reference surface S (in Fig. 1 shown). Since the condenser lenses 14 are formed on the surface 53a of the third light-transmitting element 53, the step of forming the condenser lenses 14 and the step of positioning the condenser lenses 14 and the third apertures 33 are separate steps, and thus the accuracy in positioning the condenser lenses 14 and the third apertures 33 can be improved.

[0121] In the image reading device 130, there is no light-shielding element between the third light-transmitting element 53 and the condenser lenses 14. Therefore, stray light occurs unless light beams L11 and L12, which pass both ends of the third apertures 33 in light beams passing through the third apertures 33, are contained within the area of ​​the aperture diameter of the condenser lenses 14.

[0122] Light beams L11 and L12 are light beams whose scattering in the X-axis direction gradually increases as the distance from the third apertures 33 in the +Z-axis direction increases. Thus, with increasing thickness t3 of the third transparent element 53, the scattering of backlight from light beams L11 and L12 also increases. Since, in this context, the thickness t3 of the third transparent element 53 is sufficiently thin in the image reading device 130, light beams L11 and L12 lie within the effective diameter of the condenser lens 14a. Therefore, an image unaffected by stray light can be acquired in the image reading device 130. The thickness t3 of the third transparent element 53 is smaller than the thickness t2 of the second transparent element 52 and is, for example, 210 µm.Since the light beams L11 and L12 are contained within the effective diameter of the condenser lenses 14, not only can the configuration be used in which the thickness t3 of the third light-transmitting element 53 is reduced, but also a configuration in which the aperture width of the third apertures 33 is reduced.

[0123] With regard to the other aspects, the image reading device 130 according to the variant of the first embodiment is the same as the image reading device 100 according to the first embodiment. SECOND VERSION

[0124] Fig. Figure 26 is a perspective view schematically illustrating a configuration of an optical imaging unit 201 of an image reading device 200 according to a second embodiment. Fig. 26 denote the same reference symbols as those in Fig. 1 the same or corresponding components as those in Fig. The image reading device 200 differs from the image reading device 100 according to the first embodiment in that it also has a fourth light-shielding element 15.

[0125] As in Fig. As shown in Figure 26, in the optical imaging unit 201 of the image reading device 200, the fourth light-shielding element 15 is arranged between the first light-shielding element 11 and the second light-shielding element 12. The fourth light-shielding element 15 comprises a plurality of fourth apertures 35. The plurality of fourth apertures 35 are arranged such that each corresponds to the plurality of first apertures 31 and each corresponds to the plurality of second apertures 32. The plurality of fourth apertures 35 are arranged in two rows. The plurality of fourth apertures 35 are arranged in the X-axis direction. The plurality of fourth apertures 35 are arranged in an offset pattern. Viewed in the Z-axis direction, the plurality of fourth apertures 35 overlap each of the plurality of first apertures 31 and each overlap each of the plurality of second apertures 32.In the image reading device 200, the reflected light that has passed through the third openings 33 passes successively through the second openings 32, the fourth openings 35 and the first openings 31 in this order and enters the light-receiving pixels 10.

[0126] The first light-transmitting element 251 is formed by bonding a plurality of (in this example, two) glass plates 251a and 251b, for example, with an adhesive. A first light-blocking element 11 is provided on a surface of the glass plate 251a facing the light-receiving pixels 10, and a second light-blocking element 12 is provided on a surface of the glass plate 251b facing the condenser lenses 14. The fourth light-blocking element 15 is provided between the glass plates 251a and 251b. The fourth light-blocking element 15 can be formed on either the surface of the glass plate 251a facing the condenser lenses 14 or the surface of the glass plate 251b facing the light-receiving pixels 10.

[0127] In the first embodiment, where the first translucent element 51 is formed from a single glass plate, the thickness t1 of the first translucent element 51 must satisfy the conditions expressed by equations (4) and (9) to suppress the occurrence of stray light. On the other hand, in the second embodiment, since the fourth light-blocking element 15 is arranged between the first light-blocking element 11 and the second light-blocking element 12, and the first translucent element 251 is formed by the glass plates 251a and 251b, the thickness t1 of the first translucent element 51 does not need to satisfy the conditions expressed by equations (4) and (9).

[0128] A plurality of light-blocking elements can be arranged between the first light-blocking element 11 and the second light-blocking element 12. That is, the first light-transmitting element 251 can be formed from three or more glass plates, and another light-blocking element can be provided between adjacent glass plates.

[0129] With regard to the other aspects, the image reading device 200 according to the second embodiment is the same as the image reading device 100 according to the first embodiment.

[0130] The image reading device 200 according to the second embodiment can achieve the same advantages as the image reading device 100 according to the first embodiment.

[0131] Since, in the image reading device 200 according to the second embodiment, the fourth light-shielding element 15 is arranged between the first light-shielding element 11 and the second light-shielding element 12, reflected light that has passed through the second openings 32, the fourth openings 35, and the first openings 31, which correspond to the light-receiving pixels 10, enters the light-receiving pixels 10, even if the distance between openings adjacent to each other in the X-axis direction is reduced. As a result, a high-resolution image can be acquired in the image reading device 200 according to the second embodiment. THIRD VERSION

[0132] Fig. Figure 27 is a perspective view schematically illustrating a configuration of an optical imaging unit 301 of an image reading device 300 according to a third embodiment of the present invention. Fig. 27 denote the same reference symbols as those in Fig. 1 the same or corresponding components as those in Fig. 1 shown. The image reading device 300 differs from the image reading device 100 according to the first embodiment by the arrangement of light-receiving pixels and the arrangement of openings.

[0133] As in Fig. As shown in Figure 27, in the optical imaging unit 301 of the image reading device 300, a plurality of light-receiving pixels 310 are arranged in a row. A plurality of first apertures 331 are arranged in a row. A plurality of second apertures 332 are arranged in a row. A plurality of third apertures 333 are arranged in a row. A plurality of condenser lenses 314 are arranged in a row. Accordingly, a manufacturing process for the image reading device 300 can be simplified.

[0134] In the third embodiment, to obtain an image with a resolution of 200 dpi, the spacing p (i.e., the distance between adjacent light-receiving pixels 310) of the light-receiving pixels 310 must be set to 126 µm, which corresponds to 1 / 2 of the spacing (i.e., the distance between adjacent light-receiving pixels 10) in the first embodiment. Here, in the third embodiment, a thickness t1 of a first light-transmitting element 351, which is necessary to obtain an image that is not affected by stray light, is taken into account.If half the width X0 = 31.5 µm of the light-receiving pixels 310, the refractive index n = 1.52 of the first light-transmitting element 51, half the aperture width X1 = 20.0 µm of the first apertures 331, half the aperture width X2 = 20.0 µm of the second apertures 332, and the distance t0 = 100 µm from the light-receiving pixels 310 to the first apertures 331 are substituted into equations (4) and (9) described in the first embodiment, equation (36) is derived. 93.6 μm≤t1≤98.4 μm(36)

[0135] Therefore, in the image reading device 300 according to the third embodiment, the thickness t1 of the first light-transmitting element 351 must satisfy equation (36) in order to acquire an image that is not affected by stray light.

[0136] In the third embodiment, to obtain an image with a resolution of 100 dpi, it is necessary that the half width X0 of light-receiving pixels 310 is 31.5 µm, the refractive index n of the first light-transmitting element 351 is 1.52, the half aperture width X1 of the first apertures 331 is 24.0 µm, the half aperture width X2 of the second apertures 332 is 38.0 µm, the half aperture width X3 of the third apertures 333 is 850 µm, the distance t0 from the light-receiving pixels 310 to the first apertures 331 is 250 µm, and the thickness t2 of the second light-transmitting element 52 is 700 µm.

[0137] With regard to aspects other than those described above, the image reading device 300 according to the third embodiment is the same as the image reading device 100 according to the first embodiment.

[0138] The image reading device 300 according to the third embodiment can achieve the same advantages as the image reading device 100 according to the first embodiment.

[0139] Accordingly, in the image reading device 300 according to the third embodiment, a manufacturing process of the image reading device 300 can be simplified. FOURTH VERSION

[0140] Fig. Figure 28 is a perspective view schematically illustrating a configuration of an optical imaging unit 401 of an image reading device 400 according to a fourth embodiment of the present invention. Fig. 28 denote the same reference symbols as those in Fig. 1 the same or corresponding components as those in Fig. Figure 1. The image reading device 400 differs from the image reading device 100 according to the first embodiment in the arrangement of the light-receiving pixels, the arrangement of the first aperture, the arrangement of the second aperture, the arrangement of the third aperture, and the arrangement of the condenser lenses. Accordingly, the document 6 does not need to be transported, and two-dimensional image information can be acquired from the stationary document 6.

[0141] As in Fig. As shown in Figure 28, in the optical imaging unit 401 of the image reading device 400, a plurality of light-receiving pixels 410 are arranged in a matrix, i.e., in columns and rows. A plurality of first apertures 431 are arranged in a matrix. A plurality of second apertures 432 are arranged in a matrix. A plurality of third apertures 433 are arranged in a matrix. A plurality of condenser lenses 414 are arranged in a matrix.

[0142] With the exception of the aspects described above, the image reading device 400 according to the fourth embodiment is the same as the image reading device 100 according to the first embodiment.

[0143] The image reading device 400 according to the fourth embodiment can achieve the same advantages as the image reading device 100 according to the first embodiment.

[0144] In the image reading device 400 according to the fourth embodiment, the document 6 does not need to be transported, and two-dimensional image information can be acquired from the stationary document 6. COMMERCIAL APPLICABILITY

[0145] The image reading devices according to the first to fourth embodiments are applicable to copying machines, invoice readers, and so on. DESCRIPTION OF REFERENCE MARK

[0146] 6 Document, 10, 310, 410 light-receiving pixel, 11 first light-shielding element, 12 second light-shielding element, 13 third light-shielding element, 14, 14a, 314, 414 condenser lens, 15 fourth light-shielding element, 31, 331, 431 first aperture, 32, 332, 432 second aperture, 33, 333, 433 third aperture, 35 fourth aperture, 51, 251, 351 first light-transmitting element, 52 second light-transmitting element, 53 third light-transmitting element, 100, 110, 120, 130, 200, 300, 400 image reading device, F focal point, S reference surface.

Claims

[1] Image reading device (100, 110, 120, 130, 200, 300, 400), comprising: a plurality of light-receiving pixels (10) arranged in a predetermined arrangement direction and configured to receive light reflected from an imaging object (6), the imaging object (6) being placed on a predetermined reference surface (S); a first light-shielding member (11) having a plurality of first openings (31) and disposed between the plurality of light-receiving pixels (10) and the reference surface (S); a second light-shielding member (12) having a plurality of second openings (32) and disposed between the plurality of first openings (31) and the reference surface (S); a plurality of condenser lenses (14) arranged between the plurality of second openings (32) and the reference surface (S) and arranged at a distance from the plurality of second openings (32), a first light-transmitting element (51) arranged between the first light-shielding element (11) and the second light-shielding element (12); and a second light-transmitting member (52) disposed between the second light-shielding member (12) and the plurality of condenser lenses (14); wherein the plurality of first openings (31) are arranged so that they each correspond to the plurality of light-receiving pixels (10), the plurality of second openings (32) are arranged so that they each correspond to the plurality of light-receiving pixels (10), the plurality of condenser lenses (14) are arranged so that they each correspond to the plurality of light-receiving pixels (10), the plurality of condenser lenses (14), the second light-shielding element (12), the first light-shielding element (11), and the plurality of light-receiving pixels (10) are arranged at positions at which the reflected light entering each light-receiving pixel (10) of the plurality of light-receiving pixels (10) successively passes through one of the plurality of condenser lenses (14) corresponding to the respective light-receiving pixel (10), one of the plurality of second openings (32) corresponding to the respective light-receiving pixel (10), and one of the plurality of first openings (31) corresponding to the respective light-receiving pixel (10), and enters the respective light-receiving pixel (10), and t2>n⋅t0−t1 wherein t0 denotes a distance between the plurality of light-receiving pixels (10) and the first light-shielding element (11), t1 denotes a thickness of the first light-transmitting element (51), t2 denotes a thickness of the second light-transmitting element (52), and n denotes a refractive index of each of the first light-transmitting element (51) and the second light-transmitting element (52). [2] The image reading device (130) according to claim 1, further comprising a third light-transmitting member (53) disposed between the second light-transmitting member (52) and the plurality of condenser lenses (14), the plurality of condenser lenses (14) being disposed on the third light-transmitting member (53). [3] The image reading device (100, 110, 120, 130, 200, 300, 400) according to claim 1, further comprising a third light-shielding member (13) having a plurality of third openings (33) and disposed between the second light-shielding member (12) and the plurality of condenser lenses (14), the plurality of third openings (33) being arranged to correspond to the plurality of light-receiving pixels (10), respectively. [4] Image reading device (100, 110, 120, 200, 300, 400) according to claim 3, wherein: the plurality of condenser lenses (14) are arranged on the third light-shielding member (13), and an opening width of each of the plurality of third openings (33) is smaller than an effective diameter of each of the plurality of condenser lenses (14). [5] Image reading device (100, 110, 120, 130, 200, 300, 400) according to claim 3 or 4, wherein: t2 <MAX{M1,M2} where X0 denotes a width of 1 / 2 a width of each of the plurality of light-receiving pixels (10) in the arrangement direction, X1 denotes a width of 1 / 2 an opening width of each of the plurality of first openings (31) in the arrangement direction, X2 denotes a width of 1 / 2 an opening width of each of the plurality of second openings (32) in the arrangement direction, X3 denotes a width of 1 / 2 an opening width of each of the plurality of third openings (33) in the arrangement direction, and p denotes a distance between center positions of every two of the plurality of light-receiving pixels (10) that are adjacent to each other in the arrangement direction, M1=(n⋅t0⋅(p−X3−X1) / (X0+X1))−t1, and M2=(n⋅t0+t1)⋅(p−X3−X2) / (X0+X2). [6] Image reading device (100, 110, 120, 130, 200, 300, 400), comprising: a plurality of light-receiving pixels (10) arranged in a predetermined arrangement direction and configured to receive light reflected from an imaging object (6), the imaging object (6) being placed on a predetermined reference surface (S); a first light-shielding member (11) having a plurality of first openings (31) and disposed between the plurality of light-receiving pixels (10) and the reference surface (S); a second light-shielding member (12) having a plurality of second openings (32) and disposed between the plurality of first openings (31) and the reference surface (S); a third light-shielding member (13) disposed between the second light-shielding member (12) and the plurality of condenser lenses (14); a plurality of condenser lenses (14) arranged between the plurality of second openings (32) and the reference surface (S) and arranged at a distance from the plurality of second openings (32); a first light-transmitting element (51) arranged between the first light-shielding element (11) and the second light-shielding element (12); and a second light-transmitting member (52) disposed between the second light-shielding member (12) and the plurality of condenser lenses (14); wherein the plurality of first openings (31) are arranged so that they each correspond to the plurality of light-receiving pixels (10), the plurality of second openings (32) are arranged so that they each correspond to the plurality of light-receiving pixels (10), the plurality of condenser lenses (14) are arranged so that they each correspond to the plurality of light-receiving pixels (10), the plurality of third openings (33) are arranged so that they each correspond to the plurality of light-receiving pixels (10), the plurality of condenser lenses (14), the second light-shielding element (12), the first light-shielding element (11), and the plurality of light-receiving pixels (10) are arranged at positions where the reflected light entering each light-receiving pixel (10) of the plurality of light-receiving pixels (10) successively passes through one of the plurality of condenser lenses (14) corresponding to the respective light-receiving pixel, one of the plurality of second openings (32) corresponding to the respective light-receiving pixel (10), and one of the plurality of first openings (31) corresponding to the respective light-receiving pixel (10), and enters the respective light-receiving pixel (10), and t2 <MAX{M1,M2} where t0 denotes a distance between the plurality of light-receiving pixels (10), t1 denotes a thickness of the first light-transmitting element, t2 denotes a thickness of the second light-transmitting element, n denotes a refractive index of both the first light-transmitting element and the second light-transmitting element, X0 denotes a width of 1 / 2 a width of each of the plurality of light-receiving pixels (10) in the arrangement direction, X1 denotes a width of 1 / 2 an opening width of each of the plurality of first openings (31) in the arrangement direction, X2 denotes a width of 1 / 2 an opening width of each of the plurality of second openings (32) in the arrangement direction, X3 denotes a width of 1 / 2 an opening width of each of the plurality of third openings (33) in the arrangement direction, and p denotes a distance between center positions of each two of the plurality of light-receiving pixels (10) adjacent to each other in the arrangement direction, M1=(n⋅t0⋅(p−X3−X1) / (X0+X1))−t1, and M2=(n⋅t0+t1)⋅(p−X3−X2) / (X0+X2). [7] Image reading device (100, 110, 120, 130, 200, 300, 400) according to claim 1 or 2, wherein: a thickness t1 of the first translucent element (51) satisfies: t1 <n2−1⋅(p−X1−X2) wherein X1 denotes a width of 1 / 2 an opening width of each of the plurality of first openings (31) in the arrangement direction, X2 denotes a width of 1 / 2 an opening width of each of the plurality of second openings (32) in the arrangement direction, and p denotes a distance between center positions of every two of the plurality of light-receiving pixels (10) adjacent to each other in the arrangement direction. [8] Image reading device (100, 110, 120, 130, 200, 300, 400) according to claim 7, wherein: a thickness t1 of the first translucent element (51) satisfies: t1>(X1+X2)⋅n2−1+n2⋅t02(p−X1−X0)2 where X0 denotes a width of 1 / 2 a width of each of the plurality of light-receiving pixels (10) in the arrangement direction. [9] The image reading device (100, 110, 120, 130, 200) according to any one of claims 3 to 8, wherein the plurality of light-receiving pixels (10) are arranged in an offset pattern. [10] The image reading device (300) according to any one of claims 3 to 8, wherein the plurality of light-receiving pixels (10) are arranged in a row. [11] The image reading device (400) according to any one of claims 3 to 8, wherein the plurality of light-receiving pixels (10) are arranged in a matrix. [12] The image reading device (200) according to any one of claims 1 to 6, further comprising a fourth light-shielding member (15) having a plurality of fourth openings (35) and disposed between the first light-shielding member (11) and the second light-shielding member (12), the plurality of fourth openings (35) being arranged to correspond to the plurality of first openings (31) respectively and to correspond to the plurality of second openings (32) respectively.

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