Optical device, image sensor, and method for manufacturing optical device

Abstract

An optical device (1a) has a lens array (10) and a transparent dielectric array (20). The lens array (10) includes a plurality of lenses (11). In a lens array (10), a plurality of lenses (11) are arranged such that the optical axes thereof are substantially parallel to each other. The transparent dielectric array (20) comprises a plurality of transparent dielectrics (21). In the transparent dielectric array (20), a plurality of transparent dielectrics (21) are arranged such that the central axes thereof are substantially parallel to each other. The lens array (10) and the transparent dielectric array (20) are arranged such that the optical axis of the lens (11) and the central axis of the transparent dielectric (21) are substantially parallel and the end surface of the lens array (10) and the end surface of the transparent dielectric array (20) face each other.

Description

Technical Field

[0001] The present invention relates to an optical device, an image sensor and a method for manufacturing the optical device. Background Art

[0002] In the past, it is known that there is a lens array formed by arranging and integrating a plurality of lenses in a predetermined direction in a manner that the optical axes or central axes of the lenses are parallel to each other. In such a lens array, the image information about the object surface is formed by overlapping the images obtained by each single lens, thereby obtaining small and two-dimensional image information. Utilizing such characteristics and functions, the lens array is used in an image sensor together with an array of light-receiving elements such as an illumination device and a photodiode (PD) array. As an image sensor using a lens array, for example, there is a contact image sensor (CIS).

[0003] Compared with a scanner with a reduced optical imaging method that has two-dimensional sensors such as Charge-Coupled Device (CCD) and Complementary Metal-Oxide Semiconductor (CMOS), multiple lenses and reflectors, an image sensor with a lens array has the following advantages: the distance between the object and the light receiving element (shooting element), the distance between the object point and the image point, or the distance between the object plane and the image plane is short, which makes it easy to save space; the number of components is small, and the maintainability is good; and it is easy to assemble.

[0004] The lens array used in devices such as contact image sensors has the advantages of being small, low-cost, and easy to obtain high-resolution and high-contrast images. On the other hand, the depth of field of the lens array tends to be small. Therefore, for example, when capturing images of objects with large unevenness, such as the page spread of a book, photos protected by a transparent shell, or objects far from the manuscript table, the image quality may deteriorate.

[0005] For example, as a method for improving the depth of field, Patent Document 1 describes that an overlapping limiting component having a plurality of openings corresponding to a plurality of lens elements is provided in a lens array. The optical axis of each lens element of the lens array is consistent with the center of the opening. According to this method, it can be considered that if the optical axis of the lens element is inconsistent with the center of the opening of the overlapping limiting component, the overlapping limiting component cannot reduce the imaging field of the lens and cannot reduce the overlap between images. On the other hand, it can be considered that it is difficult to arrange a plurality of lens elements exactly relative to an ideal arrangement in the manufacture of the lens array.

[0006] Patent document 2 describes a method in which, in a contact image sensor, a light-shielding mask having a diffraction effect is disposed on a surface located between an original surface and a light-receiving element array and perpendicular to the optical axis of a lens array. In this method, it is believed that a problem may arise in that high-frequency components, which are important from the perspective of fine resolution, are difficult to reflect in an image.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Laid-Open No. 6-342131

[0010] Patent Document 2: Japanese Patent Application Laid-Open No. 10-173862 Summary of the invention

[0011] Problems to be solved by the invention

[0012] In view of the above-mentioned problems, the present invention provides an optical device which is advantageous from the viewpoint of acquiring an image with a high resolution even if the subject has unevenness or height differences.

[0013] Means for solving problems

[0014] The present invention provides an optical device, which comprises: a lens array, which includes a plurality of lenses, and the plurality of lenses are arranged in a manner that the optical axes of the plurality of lenses are roughly parallel to each other; and a transparent dielectric array, which includes a plurality of transparent dielectrics, and the central axes of the plurality of transparent dielectrics are arranged in a manner that the lens array and the transparent dielectric array are roughly parallel to each other, and are configured in a manner that the optical axis and the central axis are roughly parallel and the end face of the lens array is opposite to the end face of the transparent dielectric array.

[0015] In addition, the present invention provides an image sensor having the above optical device.

[0016] Effects of the Invention

[0017] The above optical device is advantageous in that it can obtain an image with a higher resolution even if the subject has unevenness or height differences. In addition, the above optical device is also advantageous in that it has a greater depth of field than when a lens array is used alone. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a perspective view showing an example of the optical device of the present invention.

[0019] Figure 2 This is a schematic perspective view showing an example of a lens array related to the present invention.

[0020] Figure 3 It is a diagram showing the relationship between the object plane and the image plane of the lens array.

[0021] Figure 4 This is a diagram for explaining image formation by a rod lens having a refractive index distribution.

[0022] Figure 5A This is a diagram for explaining the image forming state of two adjacent rod lenses when the position of the object is at a conjugate position.

[0023] Figure 5B This is a diagram for explaining the image forming state of two adjacent rod lenses when the position of an object deviates from a conjugate position.

[0024] Figure 6 Schematically shows the diffusion of light rays that can be received at a position separated by a distance r from the central axis on the light incident surface of the rod lens.

[0025] Figure 7 : is a graph schematically showing the relationship between the angle θ determined by the definition of the aperture of the rod lens and the distance r from the central axis.

[0026] Fig. 8A FIG. 1 is a diagram schematically showing the diffusion of light in the absence of a transparent dielectric array.

[0027] Figure 8B This is a diagram schematically showing the limitation of the field of view when a transparent dielectric is arranged along the optical axis direction of the rod lens.

[0028] Figure 8C This is a diagram schematically showing the limitation of the field of view when a transparent dielectric is arranged along the optical axis direction of the rod lens.

[0029] Fig.8D This is a diagram schematically showing the limitation of the field of view when a transparent dielectric is arranged along the optical axis direction of the rod lens.

[0030] Fig. 9 This is a perspective view showing an example of the transparent dielectric array of the present invention.

[0031] Fig. 10A 2 is a diagram showing an optical system composed of a rod lens array.

[0032] Fig. 10B 2 is a diagram showing an optical system composed of a rod lens array.

[0033] Fig. 10C 2 is a diagram showing an optical system composed of a rod lens array and a transparent dielectric array.

[0034] Fig. 10D2 is a diagram showing an optical system composed of a rod lens array and a transparent dielectric array.

[0035] Fig.11 The rms ratio of the root mean square of the light aberration in the optical system composed of the rod lens array and the transparent dielectric array is shown. r With P 1 / P 0 A curve graph of the relationship.

[0036] Fig. 12A The ratio rms of the rms aberration of light rays in the optical system composed of the rod lens array α and the transparent dielectric array is shown. r and H / (n 1 ·L 01 )’s relationship curve.

[0037] Fig. 12B is a ratio showing the rms of the ray aberration in the optical system composed of the rod lens array β and the transparent dielectric array. r and H / (n 1 ·L 01 )’s relationship curve.

[0038] Fig. 12C The ratio rms of the rms aberration of light rays in the optical system composed of the rod lens array γ and the transparent dielectric array is shown in FIG. r and H / (n 1 ·L 01 )’s relationship curve.

[0039] Fig.13 is a graph showing the ratio of H / (n 1 ·L 01 ) th With P 1 / P 0 A curve graph of the relationship.

[0040] Fig.14 The relationship between the illumination unevenness ΔI and H / (n 1 ·L 01 )’s relationship curve.

[0041] Fig.15A This is a diagram showing an example of the image sensor of the present invention.

[0042] Fig. 15B It is a diagram showing another example of the image sensor of the present invention.

[0043] Fig. 15CThis is a diagram showing still another example of the image sensor of the present invention. DETAILED DESCRIPTION

[0044] Hereinafter, embodiments of the present invention will be described. In addition, the following description is for illustration of the present invention, and the present invention is not limited to the following embodiments.

[0045] Figure 1 1 is a perspective view showing an example of an optical device of the present invention. Figure 1 As shown, the optical device 1a has a lens array 10 and a transparent dielectric array 20. The directions shown by x, y and z represent the directions of the x, y and z axes of the orthogonal coordinate system. The lens array 10 includes a plurality of lenses 11. In the lens array 10, the plurality of lenses 11 are arranged only along the x direction (arranged in one row) in such a manner that their optical axes are approximately parallel to each other. For example, when the plurality of lenses 11 are observed in a direction perpendicular to the optical axis of a specific lens 11, the optical axis of the specific lens 11 is approximately parallel to the optical axes of the other lenses 11. The transparent dielectric array 20 includes a plurality of transparent dielectrics 21. In the transparent dielectric array 20, the plurality of transparent dielectrics 21 are arranged in the x direction and the y direction in such a manner that their central axes are approximately parallel to each other. In the transparent dielectric array 20, the transparent dielectrics 21 are arranged in two rows in the y direction and are arranged in a larger and longer manner in the x direction (arranged in two rows). In addition, the transparent dielectric array 20 can also be said to be composed of a lens row obtained by arranging the transparent dielectrics 21 in one row in the x direction and overlapping two layers in the y direction. For example, when observing a plurality of transparent dielectrics 21 in a direction perpendicular to the central axis of a particular transparent dielectric 21, the central axis of the particular transparent dielectric 21 is approximately parallel to the central axes of the other transparent dielectrics 21. The lens array 10 and the transparent dielectric array 20 are configured in such a manner that the optical axis of the lens 11 and the central axis of the transparent dielectric 21 are approximately parallel and the end face of the lens array 10 is opposite to the end face of the transparent dielectric array 20. By combining the lens array 10 and the transparent dielectric array 20 in such a configuration, an optical device 1a is obtained. For example, when observing the lens array 10 and the transparent dielectric array 20 in a direction perpendicular to the central axis of the transparent dielectric 21, the optical axis of the lens 11 extends in a direction parallel to the central axis of the transparent dielectric 21. Here, a plurality of axes or objects being approximately parallel to each other means that the angle formed by them is less than 1°.

[0046] In a lens array, a plurality of lenses having a light-gathering function can be arranged in one or two dimensions in such a way that their central axes or optical axes are roughly parallel. Lens arrays are widely used in optical systems for acquiring images in devices such as fax machines, copiers, and printers. As lenses used in lens arrays, end-face refractive lenses are known. In an end-face refractive lens, at least one of the end faces of the light incident end face and the light emitting end face is a curved surface, and light focusing is generated by the refraction of the end face.

[0047] In addition, as a lens for a lens array, a refractive index distribution type rod lens is also known. The refractive index distribution type rod lens (hereinafter, sometimes referred to as "rod lens") is, for example, a dielectric that can transmit light, which is composed of a cylindrical resin or glass, and has a refractive index distribution in which the refractive index decreases from the center to the periphery. Even if the rod lens does not form a part or all of the surface for light incidence and emission as a curved surface like the end face refractive lens, it can also play the function of focusing or light divergence. The rod lens does not require the curved surface processing of the end face directly related to the increase in manufacturing cost, and is easy to be processed smaller, so it can be used as a focusing lens for optical communication. In addition, in a lens array arranged in a manner that the central axes of a plurality of rod lenses are roughly parallel to each other, a linear or planar object can be imaged on the focusing surface. Therefore, such a lens array can play a high optical performance such as high resolution or high contrast, and has outstanding good characteristics such as miniaturization, low cost and high operability. In particular, a lens array having glass rod lenses tends to have significantly high weather resistance and long-term reliability. Such a lens array can be applied to many technical fields.

[0048] In the lens array 10, the lens 11 is, for example, a rod lens having a refractive index distribution in the radial direction. In this case, the lens 11 may be made of resin or glass. The lens 11 may preferably be made of glass. The lens 11 may also be an end-face refractive lens.

[0049] The arrangement of the plurality of lenses 11 in the lens array 10 is not limited to a specific method. In the lens array 10, the lens 11 is, for example, a single lens having a focusing effect, and the plurality of lenses 11 are arranged along at least one direction. The arrangement of the plurality of lenses 11 in the lens array 10 may be a one-dimensional arrangement of 1×n (n is an integer greater than 2), or a two-dimensional arrangement of m×l (m and l are integers greater than 2). Sometimes the arrangement of 1×n is referred to as a one-column arrangement, the arrangement of 2×l is referred to as a two-column arrangement, the arrangement of 3×l is referred to as a three-column arrangement, etc., in which case m (m=1, 2, 3...) is referred to as the number of columns. The arrangement of the plurality of lenses 11 in the lens array 10 may be an arrangement in which the points corresponding to the optical axes of the plurality of lenses 11 become the vertices of a square or a rectangle when the plurality of lenses 11 are observed in a direction parallel to the optical axis, or may be the densest arrangement. In the case where the plurality of lenses 11 are arranged in a row, the direction corresponding to the above-mentioned n may also be determined as the first direction or the main scanning direction. When multiple lenses 11 are arranged in two dimensions, the direction corresponding to the larger of m and l can be determined as the first direction or the main scanning direction. The direction perpendicular to the optical axis or the central axis of the lens 11 and perpendicular to the first direction (main scanning direction) can also be determined as the sub-scanning direction.

[0050] Figure 2 FIG. 1 is a schematic perspective view showing an example of the lens array 10. Figure 2 As shown, in the lens array 10, the lens 11 is, for example, a rod lens, and a plurality of lenses 11 are arranged in a row. Figure 2 In the figure, x, y and z represent the directions of the x, y and z axes of the orthogonal coordinate system. The x direction is set as the main scanning direction, the y direction is set as the sub-scanning direction, and the central axis of the lens 11 is parallel or substantially parallel to the z direction. In addition, the following description of the lens array having a plurality of rod lenses is also applicable to other lens arrays as long as there is no technical contradiction.

[0051] A plurality of lenses are arranged in the lens array, and the images formed by the plurality of lenses overlap, and a composite image is obtained corresponding to the area where the plurality of lenses are arranged. For example, when the lens array adopts an erect equal-magnification system configuration in the relationship between the object plane and the imaging plane, an erect equal-magnification image of the object plane or object point is obtained through the lens array.

[0052] Figure 3 1 is a perspective view showing another example of the lens array 10, and is a view showing the relationship between the object plane OP and the image plane IP of the lens array 10. Figure 3 , the directions indicated by x, y, and z represent the directions of the x, y, and z axes of the orthogonal coordinate system. Figure 3 The multiple lenses 11 in the lens array 10 shown are arranged in two rows with m=2. Figure 3In the figure, Z is the length of the lens 11 in the central axis direction (z direction), and L 0 is the distance between the object plane OP and the lens array 10 (the distance in the optical axis direction between the object plane OP and the end surface (light incident surface) of the lens array 10 on the side close to the object plane OP), L 1 is the distance between the lens array 10 and the image plane IP (the distance in the optical axis direction between the image plane IP and the end surface (light emitting surface) of the lens array 10 on the side close to the image plane IP), TC is given by TC = L 0 +Z+L 1 When the rod lens is cylindrical, the optical axis of the lens 11 can also be used as its central axis or the rotational symmetry axis of the rod lens. When the medium on the object side and the imaging side is the same (air, etc.) within the range of light transmission, and an erect equal-magnification system is formed in the relationship between the object plane and the imaging plane, the positional relationship between the object plane OP, the rod lens array, and the image plane IP can satisfy L 0 =L 1 You can also keep L 0 =L 1 The distance between the object plane OP or the image plane IP and the lens array 10 is adjusted to maximize the resolution of the image formed on the image plane IP. 0 , L 1 And the numerical values ​​or numerical settings of TC etc. calculated based on them correspond to the regular conjugate configuration.

[0053] If the distance between the object plane or the image plane and the lens array deviates from the regular conjugate configuration (regular configuration or upright equal-magnification system configuration), the image formed by each lens will be deviated, and the images formed by adjacent lenses will be difficult to overlap with good matching, resulting in reduced resolution. This situation is one of the main reasons for the reduced depth of field in the lens array. In the composite image formed by the lens array, the overlap m value is considered as an indicator of the degree of overlap of the images obtained by a single lens. Figure 3 In the example, the field of view radius of the normal conjugate position of the single lens is set to X 0 [mm], the distance between the optical axes or central axes of adjacent lenses in the lens array (arrangement pitch) is set to P 0 [mm], the overlap m is m = X 0 / P 0 Indicates. Figure 3 As shown, the field of view radius X 0Represents the radius of the area that can be captured by a single lens in the object plane OP. A larger overlap m means that there are more lenses that contribute to the formation of a synthetic image per unit area in the image plane IP of the lens array. Therefore, the larger the overlap m, the greater the impact of the image deviation caused when the distance between the object plane OP or the image plane IP and the lens array 10 deviates from the regular conjugate configuration when erected with equal magnification, and the synthetic image obtained by the lens array is easily blurred, and the resolution is easily reduced. In addition, Figure 3 , the case where the lenses 11 are arranged in two rows (m=2) is shown, but the same applies to the case where the lenses 11 are arranged in one row or the case where the lenses 11 are arranged in a row number exceeding two rows.

[0054] Figure 4 This is a diagram for explaining the imaging of a rod lens having a refractive index distribution. A light receiving element of an image sensor can be provided on the image plane IP of the rod lens 11, and an object having a surface such as a manuscript or a workpiece can be provided on the object position or object plane. As described above, when the lens array forms an erect and equal-magnification optical system, the object plane and the image plane become a plane that satisfies L 0 =L 1 The conditions for the conjugation of positive equal-fold systems (normal) are related. In this case, if Figure 4 As shown, the equal magnification image I is obtained. U When the object or the surface of the object changes from satisfying L 0＝ L 1 The condition for the conjugate position P C The offset changes as L 1 <L 0 When the relationship is such that the reduced image I is formed in the imaging plane IP (imaging position) R (Upright reduction system). This is because the field of view of a single lens with a given aperture angle varies with L. 0 The ratio of the object to the field of view radius changes.

[0055] The object position in the lens array changes from satisfying L 0 =L 1 If the position of the conjugate of the condition changes, the following inconvenience may further occur. Figure 5A This is a diagram for explaining the image formation state of adjacent rod lenses when the position of the object is at a conjugate position. Figure 5B This diagram explains the image formation state of adjacent rod lenses when the position of the object deviates from the conjugate position. Figure 5A and Figure 5B In the image, a character such as "A" is imaged on the image plane through two adjacent single lenses.

[0056] like Figure 5A As shown, when L 0=L 1 When the relationship holds, each single lens captures a portion of a character such as "A" in its field of view, forming an image of the same size as the object on the image plane, and the composite images formed by the two single lenses overlap in a manner that does not cause deviation. Figure 5B As shown, when the object moves from L 0 =L 1 When the positions where the conjugate relationship of L is established are offset, the image formed by the two single lenses becomes a reduced image. 1 is constant, so the position and size of the circular image formed by the single lens on the image plane do not change. Therefore, the positional relationship between an object such as "A" and the image formed by two adjacent single lenses deviates, and mismatch may occur in the composite image formed by the two single lenses. Therefore, a reduction in resolution may occur.

[0057] In this way, it can be understood that the closer the position of the object is to L, the closer it is to L. 0 The larger the directional deviation, the lower the magnification of the image formed by the single lens, and the lower the resolution is, which is the main reason why the depth of field of the lens array is small. Figure 4 , Figure 5A as well as Figure 5B In the description, the case where the single lens in the lens array is a rod lens is used as an example for explanation. The same problem may also occur in the case where the single lens in the lens array is an end-face refractive lens whose incident surface and exit surface of light are composed of surfaces including curved surfaces. In addition, there is also the following optical system: two or more lenses are arranged along the optical axis direction in such a way that their optical axes are consistent to obtain a lens system (cascade arrangement), and a lens array formed by arranging the lens system along the main scanning direction constitutes an erect equal-magnification system in relationship with the object plane and the image plane. Even in the case of adopting such a lens array, the lens system arranged along the optical axis direction can be replaced with the single lens described in this specification and the same description can be applied.

[0058] As mentioned above, in a lens array, the greater the value of the overlap m, the more likely the number of lenses related to the formation of a synthetic image per unit area will increase. Therefore, the greater the value of the overlap m, the more likely the reduction in resolution caused by changes in the position, deviations, and offsets of the object will become significant. Therefore, in a lens array, the depth of field tends to decrease in proportion to the size of a parameter such as the overlap m.

[0059] The rod lens can be formed of, for example, a cylindrical transparent dielectric. The rod lens has, for example, a refractive index that decreases from the central axis toward the periphery in the radial direction. Therefore, light is bent inside the rod lens, so that, for example, even if the surface where light enters or the surface where light exits is formed flat as the end face of the rod lens, functions such as focusing can be achieved.

[0060] When the lens 11 is a rod lens, the refractive index distribution of the rod lens is fitted by, for example, the following formula (1). In addition, the aperture NA of the rod lens is represented by formula (2). In formula (1), r is the distance from the optical axis of the rod lens in the radial direction. n(r) is the refractive index of the rod lens at the distance r. n 0 is the refractive index at the optical axis or center of the rod lens. g is the refractive index distribution constant of the rod lens. 0 The effective radius of the rod lens is 1 / 2 of the effective diameter (effective diameter), which is the range through which light can pass, and is a quantity represented by the diameter of a circle around the central axis of the rod lens.

[0061] n(r) 2 =n 0 2 {1-(g·r) 2 Formula (1)

[0062] NA=n 0 ·g·r 0 Formula (2)

[0063] Figure 6 The angle θ at which light can be received at a distance r from the center of the rod lens on the light incident surface is schematically shown. Here, the angle at which light can be received is the angle of light that can contribute to imaging through the rod lens, and incident light above this angle will not be emitted from the lens due to absorption on the side wall of the rod lens, etc. Figure 6 In FIG. 1 , the range of light that can be received at a distance r is represented by a cone (Acceptance Cone) whose vertex angle is angle θ. The angle formed by the generatrix of the cone and the central axis of the cone is represented as the acceptance angle θ.

[0064] Figure 7 : is a graph schematically showing the relationship between the angle θ determined by the definition of the aperture of the rod lens in equation (2) and the distance r from the central axis. Figure 7 As shown in FIG. 1 , the light receiving angle θ at the center of the light incident surface of the rod lens with r=0 is the maximum value, and the angle θ becomes zero at the outer peripheral end of the rod lens. The maximum value of the angle θ is defined as the aperture angle θ. 0 Aperture angle θ 0 and the opening NA exists NA = sinθ 0 relationship.

[0065] The method for producing the rod lens is not limited to a specific method. The rod lens can be produced, for example, by the following methods (i), (ii), and (iii).

[0066] (i) A glass rod having a predetermined composition and a substantially circular cross section is obtained by a down-draw method.

[0067] (ii) A concentration gradient of an element such as Li is formed in the rod-shaped glass obtained in (i) by an ion exchange method, thereby forming a refractive index distribution along the radial direction of the rod-shaped glass.

[0068] (iii) The rod-shaped glass having the refractive index distribution formed thereon is cut into a predetermined length in a direction substantially perpendicular to the central axis and then polished to provide planar end faces serving as a light incident surface and a light emitting surface.

[0069] For example, the step (iii) described above includes the following (iiia) and (iiib).

[0070] (iiia) A plurality of rod-shaped glasses are arranged so that the central axes of the plurality of rod-shaped glasses are substantially parallel to each other, and the plurality of rod-shaped glasses are sandwiched by a pair of side plates.

[0071] (iiib) A plurality of rod-shaped glasses are cut approximately perpendicularly to the central axis of the rod-shaped glasses at an appropriate length capable of exhibiting the required optical performance and then polished to provide planar end faces that function as light incident faces and light emitting faces. The two end faces corresponding to the light incident faces and the light emitting faces may be parallel.

[0072] In the optical device 1 a , the transparent dielectric array 20 is arranged, for example, so as to overlap with the lens array 10 in a direction perpendicular to the optical axes of the lenses 11 of the lens array 10 .

[0073] Fig. 8A Schematic diagram showing the diffusion of light passing through the lens 11 which is a rod lens. Figure 8B , Figure 8C as well as Fig.8D The limitations of the field of view when the transparent dielectric is arranged along the optical axis direction of the rod lens 11 are schematically shown. Figures 8A to 8D In the optical system schematically shown in the drawings, the medium of the space from the object plane OP to the rod lens 11 and the medium of the space from the transparent dielectric 21 to the imaging plane IP is air (refractive index = 1), and the rod lens 11 and the transparent dielectric 21 may be in contact with each other in the optical axis direction of the rod lens 11, or a medium space composed of air may exist between the rod lens 11 and the transparent dielectric 21 in the optical axis direction of the rod lens 11. Fig. 8A In the above example, the directions indicated by x, y, and z represent the directions of the x, y, and z axes of the orthogonal coordinate system. Figure 8B to Figure 8DThe same is true in FIG. These figures show cross-sectional views on a plane including the central axis of the cylindrical rod lens 11 and the central axis of the transparent dielectric 21. In addition, in these models, a system is shown that images the object plane OP are formed on the imaging plane IP, and the object point in the object plane OP is formed as an erect equal-magnification image on the imaging plane IP by the rod lens 11 or an optical device composed of the rod lens 11 and the transparent dielectric array 20. The dotted lines in the figure indicate the range of the subject on the object plane that the optical system can capture and the range projected to the imaging plane by the optical system.

[0074] FIG. 8B to FIG. 8D The interior of the transparent dielectric 21 is transparent and does not absorb light. Or, the amount of light absorbed inside the transparent dielectric 21 is very small. The transparent dielectric 21 has a constant refractive index greater than 1 (or greater than the refractive index of air). Part or all of the light reaching the side of the transparent dielectric 21 is absorbed. In this way, light shielding can be achieved. In addition, the thickness of the portion that absorbs the light reaching the side of the transparent dielectric 21 is as small as possible, and its thickness can also be regarded as zero. In addition, in the case where a black coating for absorbing light is formed on the side of the transparent dielectric, its wall thickness can also be less than 50μm. A transparent dielectric array 20 can be formed by arranging such transparent dielectrics 21. In other words, the transparent dielectric array is obtained by arranging a plurality of transparent dielectrics that have a constant refractive index and whose sides (peripheral surfaces) absorb a portion of the light in a manner such that their central axes are roughly parallel to each other and then integrating them.

[0075] The shape of the transparent dielectric 21 is not limited to a specific shape. The transparent dielectric 21 is, for example, a column. The transparent dielectric 21 may be a cylindrical shape, or a polygonal column shape such as a quadrangular column shape or a hexagonal column shape. The transparent dielectric 21 may be an elliptical column shape, or an elongated cylindrical shape. In this case, the field of view in a specific direction is easily limited.

[0076] As a transparent dielectric with a refractive index of 1, if air is understood as a dielectric, it can be a thin-walled cylindrical shape, or it can be a transparent dielectric array (to be precise, a cylindrical array) with the central axes of the cylinders parallel and arranged in at least one direction.

[0077] exist Fig. 8A In the embodiment, the distance between the object plane OP and the light incident surface of the rod lens 11 is equal to the distance between the light exit surface of the rod lens 11 and the imaging surface IP. Figure 8B to Figure 8DOne point to note is that, since the transparent dielectric 21 has a constant refractive index, the distance between the object plane OP and the light incident plane of the rod lens 11 is different from the distance between the light exit plane of the rod lens 11 and the imaging plane IP. In addition, the light exit plane of the rod lens 11 (the surface on the opposite side of the object plane OP) and the light incident plane of the transparent dielectric array 20 (the surface on the opposite side of the imaging plane IP) may be in contact with or separated from each other.

[0078] exist Fig. 8A In the embodiment, the rod lens 11 is configured to form an erected equal-magnification image of the object point, so the aperture angle θ, which is the maximum value of the light receiving angle, is 0 In the rod lens 11, an aperture angle θ is generated at the center of the light emitting surface, where the angle θ is the maximum value. 0 Therefore, regarding the field of view limitation caused by the transparent dielectric 21, attention is paid to the light emitted from the center of the rod lens 11.

[0079] exist Fig. 8A As described above, the object plane OP, the rod lens 11, and the image plane IP are arranged at conjugate positions of the erect equal-magnification system. Fig. 8A In FIG. 1 , the dotted line schematically shows the diffusion of light corresponding to the opening of the rod lens 11. Fig. 8A In the figure, since there is no transparent dielectric 21, the field of view diameter of the object plane OP and the imaging diameter of the image plane position are in a conjugate positional relationship, and there is no obstruction, so they are the same size.

[0080] exist Figure 8B In the embodiment, first, three transparent dielectrics 21 having a diameter substantially the same as that of the rod lens are arranged in such a manner that the central axes are parallel to each other and the end faces perpendicular to the central axes of the respective transparent dielectrics 21 are coplanar, thereby forming a transparent dielectric array 20. The transparent dielectrics 21 are arranged on the imaging plane IP side of the rod lens 11 in such a manner that the central axis of one transparent dielectric 21 coincides with the extension line of the central axis of the rod lens 11 and the light exit surface of the rod lens 11 (the end face of the rod lens 11 on the side close to the imaging plane IP) and the light incident surface of the transparent dielectric 21 (the end face of the transparent dielectric 21 on the side close to the rod lens 11) are parallel and opposite to each other. The lens array 10 and the transparent dielectric array 20 satisfy the condition represented by the following formula (3), for example. In the formula (3), H is the length [mm] of the transparent dielectric 21 in the central axis direction. 1 is the refractive index of the transparent dielectric 21, 1≦n 1 , or, 1.2≦n 1 ≦2.0, or 1.4≦n 1 ≦1.8. The refractive index n in transparent dielectric 1When n is 1, the transparent dielectric can also be formed of a thin-walled cylindrical shape. In addition, by forming it from an organic-inorganic hybrid material containing hollow particles of silicon dioxide or magnesium fluoride (for example, a material composed of an alkoxysilane containing hollow particles or its hydrolyzate, a polymer or other binder), a refractive index n can be obtained. 1 A transparent dielectric with a refractive index close to 1. 1 The distance between the central axes of adjacent transparent dielectrics 21 in the transparent dielectric array 20 (transparent dielectric arrangement pitch) is [mm]. The left side is the distance between the central axes of adjacent transparent dielectrics 21 in the transparent dielectric array 20 (transparent dielectric arrangement pitch). 0 When the incident angle is 0.1° and the incident angle is 0.1°, the distance between the light exit point on the opposite surface (light exit surface) of the transparent dielectric 21 and the center of the light exit surface is calculated (using sinθ 0 ≈tanθ 0 The right side is the radius (of the end face) of the transparent dielectric 21 when adjacent transparent dielectrics 21 are arranged without a gap.

[0081] tanθ 0 ·H / n 1 >P 1 / 2 Formula (3)

[0082] exist Figure 8B In the equation (3), when the equation (3) holds, a part of the light emitted from the rod lens 11 reaches the side of the transparent dielectric 21 and is absorbed, and an image is formed by the light that does not reach the side but passes through the transparent dielectric 21. The diameter of the image formed on the image plane is smaller than the field of view diameter on the object plane OP. For example, when a plurality of transparent dielectrics 21 are arranged in the first direction (main scanning direction) in such a manner that the distance between the adjacent central axes of the plurality of transparent dielectrics 21 is equal to the diameter of the rod lens 11, the diffusion of the light corresponding to the field of view diameter of each rod lens 11 is narrowed by the side of the transparent dielectric 21, and a synthetic image is obtained in a state where the overlap degree m is substantially small.

[0083] exist Figure 8C In the embodiment, the rod lens 11 and the transparent dielectric array 20 are used Figure 8B The rod lens 11 and the transparent dielectric array 20 are the same as those used in the previous description. Figure 8B The difference between the above-described cases is that the central axis of the transparent dielectric 21 in the transparent dielectric array 20 deviates from the optical axis of the rod lens 11 by the transparent dielectric arrangement pitch P. 1half value. When such a deviation of the position of the transparent dielectric array 20 occurs, the outermost light of the rod lens is not easily blocked by the side of the transparent dielectric 21 and easily reaches the image plane IP. Therefore, the field of view of the rod lens is not easily limited by the transparent dielectric 21. When the rod lens and the transparent dielectric 21 are arranged in a manner such that the distance between the optical axes of the rod lenses and the distance between the central axes of the transparent dielectric 21 are the same in a state where there is a deviation between the central axis of the transparent dielectric 21 and the optical axis of the rod lens, the diffusion of light corresponding to the field diameter of each rod lens will not be narrowed due to the light shielding property of the side of each transparent dielectric 21 of the transparent dielectric array 20. Therefore, the overlap degree m in such a state can be substantially the same as the overlap degree m in a state where the transparent dielectric array 20 does not exist. Therefore, in a case where the diameter of the transparent dielectric 21 is equal to the diameter of the rod lens, the side of the transparent dielectric 21 can be arranged, for example, at a position in the lens array that is deviated from the optical axis of the rod lens in the arrangement direction of the rod lenses.

[0084] exist Fig.8D In the transparent dielectric arrangement spacing P 1 The diameter of the transparent dielectric 21 is smaller than the diameter of the rod lens 11. For example, the diameter of the transparent dielectric 21 is 1 / 2 of the diameter of the rod lens 11, and the transparent dielectric arrangement pitch P is 1 It is also adjusted to 1 / 2 of the diameter of the rod lens. 1 When the transparent dielectric material 21 is smaller, even if the side surface of the transparent dielectric material 21 is located near the straight line including the optical axis of the rod lens 11 in the arrangement direction of the rod lens 11 in the lens array 11, the opening of the rod lens 11 is limited. In this way, the plurality of transparent dielectric materials 21 are arranged in a manner having subdivided light-transmitting portions, and in the light-transmitting portions, the transparent dielectric material arrangement pitch P in the transparent dielectric array 20 is set to 1 The distance P between the optical axes of adjacent rod lenses is 0 The transparent dielectric array 20 has a size smaller than the diameter of the rod lens. Therefore, even if the transparent dielectric 21 is arranged in such a way that the side surface of the transparent dielectric 21 exists near the straight line containing the optical axis of the rod lens 11 in the arrangement direction of the rod lens 11 in the lens array 10, the overlap degree m is easy to become small.

[0085] like Fig.8D As shown, when the transparent dielectric is arranged at a spacing P 1When the diameter of the rod lens 11 is smaller than that of the rod lens 11, the necessity of achieving precise alignment of the optical axis of the rod lens 11 and the central axis of the transparent dielectric 21 in order to reduce the overlap m is reduced. Therefore, even if there is an error in the arrangement interval of the lenses 11 that may occur in the lens array 10, the depth of field is not likely to become unstable. In addition, the problem of not being able to achieve alignment (coaxiality) between the optical axis of the rod lens 11 and the central axis of the transparent dielectric 21 due to the difference in thermal expansion generated by each component accompanying the temperature change is also unlikely to occur.

[0086] The transparent dielectric array 20 may also include, for example, a plurality of transparent dielectrics 21 arranged in one row or two or more rows. The transparent dielectrics 21 can function as an opening limiting element. In the transparent dielectric array 20, the plurality of transparent dielectrics 21 are arranged so that their central axes are substantially parallel to each other.

[0087] Fig. 9 FIG. 2 is a perspective view showing an example of the transparent dielectric array 20. Fig. 9 In the embodiment, the transparent dielectric array 20 is composed of two columns, but the following description can also be applied to a transparent dielectric array with one column or more than two columns. A plurality of transparent dielectrics 21 are integrated between a pair of flat plates 22 by filling the gaps therebetween with resin or adhesive 23. The flat plates 22 are, for example, plates made of fiber reinforced plastic (FRP). The resin 23 is colored black. According to such a structure, for example, it is easy to arrange a plurality of transparent dielectrics 21 in a plurality of columns in the transparent dielectric array 20.

[0088] The material of the transparent dielectric 21 is not limited to a specific material. The transparent dielectric 21 can also be formed by the same type of material as the rod lens. In this case, it is not easy to produce a difference in thermal expansion between the transparent dielectric 21 and the rod lens, and it is easy to install the transparent dielectric array 20 relative to the lens array 10. In addition, the glass before and after the refractive index distribution is formed by the ion exchange method (ii) above will have some increase or decrease in metal components, but it can also be regarded as essentially the same type of material. In addition, the refractive index n at the center axis of the single lens constituting the rod lens array is 0 The refractive index n of the transparent dielectric 1 The refractive indices may be substantially the same value. The fact that a plurality of refractive indices are substantially the same value means that the absolute value of the difference between the refractive indices is less than 0.0005.

[0089] The transparent dielectric 21 can be made of, for example, a material having substantially the same refractive index n. 1 For example, the refractive index n of the transparent dielectric 21 is 1 Satisfy 1≦n 1 The condition of 1.2≦n can also be satisfied1 ≦2.0, and 1.4≦n 1 ≦1.8. The surface roughness of the side of the transparent dielectric 21 is not limited to a specific value. The surface roughness can also be adjusted in a manner that scatters part or all of the light that passes through the inside of the transparent dielectric 21 and reaches its side. For example, the arithmetic mean roughness Ra of the side of the transparent dielectric 21 is 0.1 to 5.0 μm. The arithmetic mean roughness Ra is determined in accordance with Japanese Industrial Standard JIS B0601:1994. In order to absorb part or all of the light, a coating film can also be formed on the side of the transparent dielectric 21. The coating film can be formed of a resin that is colored in a light-absorbing color such as black. The coating film can also play a role in a conventional lens (for example, an optical element composed of a concave surface, a convex surface, a plane, a diffraction grating surface, etc., which is used to refract, diffract, and diverge or converge light on these surfaces). The material for coating preferably includes curable resins such as epoxy resin, acrylic resin, polyurethane resin, phenolic resin, melamine resin, unsaturated polyester resin, alkyd resin and silicone resin, and a mixture of one or more of them can also be used. Furthermore, the material for coating preferably has a matte appearance after curing. In addition to the above-mentioned resins, the material for coating can also include black particles such as carbon black, titanium black (titanium black pigment), magnetite-type ferroferric oxide, oxides containing copper and chromium, and Valifast Black (azo-chromium compound). In addition, the original yarn of the rod lens can also be immersed in a chloroform solution containing Valifast Black (made by Orient Chemical Company), the solution is attached to the side of the original yarn, and the chloroform is evaporated and dried to make a glass rod or the original yarn of the rod lens dyed black. In addition, in the case where each lens constituting the lens array 10 is a refractive index distribution lens, the side of the transparent dielectric 21 can also be coated with the same resin as the resin used to coat the side of each lens in black.

[0090] The transparent dielectric array 20 can also be manufactured, for example, by a method including the following steps: arranging a plurality of rod-shaped glasses obtained by pulling down so that their central axes are substantially parallel; and forming a pair of faces substantially perpendicular to the central axes of the glasses to obtain the transparent dielectric 21. The transparent dielectric array 20 can be manufactured, for example, by a method including the following (I) and (II).

[0091] (I) A plurality of rod-shaped glasses manufactured by a down-draw method or the like are arranged so that no refractive index distribution is formed inside the glasses and the central axes or rotational symmetry axes of the plurality of rod-shaped glasses are substantially parallel to each other, and are clamped by a pair of plate-like side plates and integrated by an adhesive or resin or the like.

[0092] (II) A plurality of rod-shaped glasses are cut into predetermined lengths in a direction substantially perpendicular to their central axes and polished to provide end faces perpendicular to the central axes that serve as light incident surfaces and light emitting surfaces.

[0093] According to such a method, the glass composition of the transparent dielectric 21 constituting the manufactured transparent dielectric array 20 can also be made substantially the same as the glass composition of the rod-shaped glass obtained in the above (i). Therefore, the difference in the physical property values ​​such as the thermal expansion coefficient and the light transmittance between the transparent dielectric 21 and the rod-shaped lens is likely to be reduced. Since the difference in the thermal expansion coefficient between the multiple components is small, even in the case of temperature changes, the relative positional relationship between the components accompanying the expansion and contraction of the components is not likely to change, and the mutual positional accuracy of the multiple components and the change in the optical performance of the multiple components in cooperation are also likely to be reduced.

[0094] For example, the transparent dielectric 21 having a desired size may be produced by heating and stretching a glass or resin rod that has been previously molded into a predetermined shape such as a polygonal column.

[0095] For example, a resin may be filled in the gaps between the transparent dielectrics 21, and the resin may be cured to integrate the plurality of transparent dielectrics 21. In this case, the resin may be colored black to improve light absorption. The resin may be filled, for example, by supplying a liquid resin toward one end of the gap while performing vacuum suction at the other end of the gap, thereby spreading the resin throughout the gaps in the arrangement of the plurality of transparent dielectrics 21. Alternatively, a black-colored adhesive resin may be pre-coated on the surfaces of a pair of flat plates, and after arranging and sandwiching the plurality of transparent dielectrics 21 between the pair of flat plates, the pair of flat plates and the plurality of transparent dielectrics 21 may be heated and pressed to fill the gaps between the transparent dielectrics 21 with the resin.

[0096] The transparent dielectric 21 may also have a structure including a core and a cladding. In this case, the cladding may be a colored layer that absorbs a portion of light that advances toward its periphery or reaches the vicinity of the side surface of the transparent dielectric 21. It is also preferable that fine concavoconvex portions that promote scattering and absorption of light are formed on the side surface of the transparent dielectric 21.

[0097] The arrangement pattern of the plurality of transparent dielectrics 21 in the transparent dielectric array 20 is not limited to a specific pattern. The arrangement pattern of the plurality of transparent dielectrics 21 may be a one-dimensional arrangement or a two-dimensional arrangement. In the two-dimensional arrangement, the plurality of transparent dielectrics 21 are, for example, arranged in a plurality of columns. In this case, the central axes of the plurality of transparent dielectrics 21 in each column may be substantially parallel.

[0098] In the optical device 1a, the distance P 0 and transparent dielectric arrangement pitch P 1 The conditions to be satisfied are not limited to specific conditions. The optical device 1a preferably satisfies P 1 ≦0.8×P 0 Therefore, in the optical device 1a, the depth of field is easily increased, and in the device having the optical device 1a, even if the subject has unevenness and height differences, it is possible to obtain an image with less degradation and higher resolution. The optical device 1a also satisfies, for example, 0.3×P 0 ≦P 1 In addition, P 0 P is the distance between the optical axes of adjacent rod lenses 11 in the lens array 10, and is sometimes also defined as the arrangement pitch of the rod lenses or the inter-lens pitch. 1 It is the distance between the central axes of adjacent transparent dielectrics 21 in the transparent dielectric array 20, and is sometimes also defined as the arrangement pitch of the transparent dielectrics or the inter-dielectric pitch. 1 0.3×P 0 As described above, it is not easy to cover the effective diameter of the lens and it is easy to prevent the light quantity from decreasing, and the lens opening is not easy to be divided. Therefore, it is easy to prevent the NA in the sub-scanning direction (y direction) from becoming smaller and the spot diameter from becoming larger, and it is easy to prevent the side peaks (side peaks) from being generated in the scanning direction (x direction) due to the periodic structure of the transparent dielectric array. In addition, P 0 and P 1 Can meet 0.4×P 0 ≦P 1 The condition of 0.5×P can also be satisfied 0 ≦P 1 In addition, for a lens array of one column, 0.45×P 0 ≦P 1 ≦0.65×P 0 The condition of 0.5×P can also be satisfied 0 ≦P 1 ≦0.6×P 0 conditions.

[0099] In the optical device 1a, the length H [mm] of the transparent dielectric 21 in the central axis direction and the refractive index n of the transparent dielectric 21 are 1 , distance L between rod lens and object plane 01 [mm], transparent dielectric arrangement spacing P 1 and the arrangement pitch P of the rod lenses 0 The conditions to be satisfied are not limited to specific conditions. Distance L between rod lens and object plane 01It is the distance between the end face of the lens on the side close to the object plane and the object plane when an erect equal-magnification image of an object point on the object plane is formed on the imaging plane with the highest resolution in an optical system using the optical device 1a. In the optical device 1a, it is preferable to satisfy H / (n 1 ·L 01 )>0.27×(P 1 / P 0 )+0.023. As a result, the optical device 1a is more likely to have a larger depth of field, and for example, even if a subject or workpiece has thickness, unevenness, or height differences, it is easier to obtain an image with less degradation in optical performance and higher resolution.

[0100] In the optical device 1a, it is preferable to satisfy H / (n 1 ·L 01 )≦0.6. In this case, uneven illumination is less likely to occur in the optical device 1a.

[0101] When using an optical device in which a lens array and a transparent dielectric array are arranged in such a manner that the optical axes of the lenses of the lens array and the central axis of the transparent dielectric are substantially parallel, the accuracy required for the arrangement of the lenses and the transparent dielectric is an important research issue in terms of ensuring the performance of the optical device. Therefore, the influence of the deviation of the relative positions of the lenses of the lens array and the transparent dielectric of the transparent dielectric array in the x-direction and the y-direction from the ideal positions on the performance of the optical device is studied.

[0102] For the purpose of ray tracing or image evaluation, OSLO Premium rev 6, a geometric optics calculation software from Lambda Research Corporation of the United States, was used to study the effect on depth of field when the relative positions of the rod lens array and the transparent dielectric array were changed, considering an appropriate optical system model.

[0103] Fig. 10A An optical system consisting of an object plane OP, a rod lens array 10p, and an imaging plane IP is schematically shown. The object plane OP is set as a plane perpendicular to the paper surface, the point on the object plane OP at the position represented by A is set as the origin, the axis passing through the origin and perpendicular to the object plane OP and toward the imaging plane IP is set as the z-axis, the axis passing through the origin and perpendicular to the z-axis and parallel to the paper surface is set as the x-axis, and the axis passing through the origin and perpendicular to the x-axis, z-axis and the paper surface is set as the y-axis. The rod lenses 10p are arranged in a row along the x direction and are configured in such a way that the central axis of one of the rod lenses in the rod lens array 10p is consistent with a part of the z-axis. In the case of a cylindrical rod lens or a rotationally symmetrical lens, its central axis or rotationally symmetrical axis can also serve as the optical axis of the lens. Therefore, it can also be configured in such a way that the z-axis is consistent with the optical axis of the rod lens. Fig. 10A In FIG. 1 , an erect equal-magnification image IQ of an object point on the object plane OP at a position indicated by A is formed on the imaging plane IP with the highest resolution by the rod lens array 10 p. The object plane OP indicated by A, the rod lens array 10 p and the imaging plane IP are in a regular arrangement.

[0104] Fig. 10B It is observed from one side of the object plane OP along the z direction Fig. 10A The object plane OP, the rod lens array 10p and the imaging plane IP are provided in the air (refractive index = 1).

[0105] Fig. 10C The optical system consisting of an object plane OP, a rod lens array 10p, a transparent dielectric array 20p and an imaging plane IP is schematically shown. The object plane OP is set to be a plane perpendicular to the paper surface. Fig. 10C The point on the object plane OP represented by A is set as the origin, the axis passing through the origin and perpendicular to the object plane OP and toward the imaging plane IP is set as the z-axis, the axis passing through the origin and perpendicular to the z-axis and parallel to the paper surface is set as the x-axis, and the axis passing through the origin and perpendicular to the x-axis, z-axis and paper surface is set as the y-axis. The rod lenses 10p are arranged in a row along the x direction and are configured in such a way that the central axis of one of the rod lenses in the rod lens array 10p is roughly consistent with a part of the z-axis. In the case of a cylindrical rod lens or a rotationally symmetrical lens, its central axis or rotationally symmetric axis can also serve as the optical axis of the lens. Therefore, it can also be configured in such a way that the z-axis is roughly consistent with the optical axis of the rod lens. Fig. 10C The erect equal-magnification image IQ of the object point on the object plane OP at the position indicated by A is formed on the imaging plane IP with the highest resolution through the optical system composed of the rod lens array 10p and the transparent dielectric array 20p. The object plane OP at the position indicated by A, the optical device composed of the rod lens array 10p and the transparent dielectric array 20p, and the imaging plane IP are in a regular configuration.

[0106] Fig. 10D It is observed from one side of the object plane OP along the z direction Fig. 10C The object plane OP, the rod lens array 10p, the transparent dielectric array 20p and the imaging plane IP are arranged in the air (refractive index = 1). Fig. 10D As shown, the transparent dielectric array 20p is configured such that transparent dielectric arrays arranged in one row along the x direction are overlapped in the y direction with the smallest gap (arranged in two rows). The transparent dielectric array 20p is arranged such that the xz plane divides the width of the transparent dielectric array 20p in the y direction into two equal parts, and the yz plane includes the central axis of one transparent dielectric of the transparent dielectric array 20p and the central axis of the rod lens.

[0107] As described above, the object point and the image point IQ located at the origin on the object plane OP represented by A are in a conjugate positional relationship of an erect equal-magnification system. When the object plane OP is located at the position of A, the intersection of the extension of the optical axis of a specific rod lens and the object plane OP is also the origin of the coordinate system determined by the x-axis, the y-axis, and the z-axis. A point light source is set at the origin, and the image formed by the light source on the image plane IP is evaluated. It is assumed that the light source is an ideal point light source.

[0108] exist FIG. 10A to FIG. 10D In the optical system shown in FIG. 1 , the rod lens array 10 p has the optical performance shown in Table 1. In addition, L in the table 0 Indicated by Fig. 10A and Fig. 10B In the optical system composed of the rod lens array 10p, the distance between the rod lens array 10p and the object plane OP when the erect equal-magnification image of the object plane OP at the position represented by A is formed on the imaging plane IP with the highest resolution (i.e., in the regular configuration).

[0109]

Table 1

[0110] project symbol unit Specifications Number of rod lens array columns 1 Central refractive index <![CDATA[n 0 ]]> 1.600 Refractive index distribution constant g [ / mm] 0.4400 Lens period length PP=2π / g [mm] 14.28 Lens arrangement spacing <![CDATA[P 0 ]]> [mm] 0.600 Rod lens diameter <![CDATA[D 0 ]]> [mm] 0.600 Effective radius of rod lens <![CDATA[r 0 ]]> [mm] 0.285 Numerical aperture <![CDATA[NA≈n 0 ·g·r 0 ]]> 0.20 Aperture angle <![CDATA[θ 0 ]]> [deg.] 11.5 Lens length Z [mm] 7.65 Lens conjugate length TC [mm] 33.01 Lens-object plane distance <![CDATA[L 0 ]]> [mm] 12.68 The ratio of the distance between the lens and the object plane to the length of the lens period <![CDATA[L 0 / PP]]> 0.89

[0111] Composed in Fig. 10C or Fig. 10D The transparent dielectric array 20p included in the optical device shown in the figure is composed of transparent dielectrics having the same refractive index n 1 A non-absorbent cylindrical transparent dielectric composed of a medium. The dielectric is regarded as a dielectric that strictly follows Snell's law without scattering at the end face where light enters and exits. In addition, a light absorbing layer with a negligible thickness that absorbs the light that reaches the transparent dielectric is regarded as formed on the side face of the transparent dielectric.

[0112] exist Fig. 10C and Fig. 10D In the optical system shown in FIG. 1 , the rod lens array 10p is set to be the same as that recorded in Table 1. Fig. 10A and Fig. 10B The same rod lens array as that used in the optical system shown in FIG. 2 is used as the rod lens array. As for the transparent dielectric array 20p, a transparent dielectric array having the characteristics and physical quantities shown in Table 2 is prepared. Fig. 10C and Fig. 10D In the optical system including the optical device composed of the rod lens array 10p and the transparent dielectric array 20p, when an erect equal-magnification image of the object plane OP is formed on the imaging plane IP with the highest resolution (i.e., in a regular configuration), the distance between the end surface of the rod lens array 10P on the object plane OP side and the object plane OP is L. 01 .exist Fig. 10C and Fig. 10DIn the relationship shown, it can be considered that Fig. 10A and Fig. 10B In the optical system including the rod lens array 10p shown in the figure, a transparent dielectric array is inserted directly behind the rod lens array 10p, so that Fig. 10C and Fig. 10D The distance L in the regular configuration shown 01 and Fig. 10A and Fig. 10B The distance L in the regular configuration shown 0 are approximately the same value. Regarding the distance between the end face of the rod lens array and the object plane, two values ​​being approximately the same means that the absolute value of the difference between the two values ​​is less than 2% relative to the reference value. In Table 2, the transparent dielectric array 20P shown in (i) to (v) has a P value of approximately 1.1. 1 / P 0 and H / (n 1 ·L 01 ) and the like also include the relationship with the rod lens array 10p shown in Table 1 included in each optical device combined with them in the proper position.

[0113]

Table 2

[0114]

[0115] In the optical simulation, Fig. 10A and Fig. 10B When performing optical calculations on the optical system composed of the rod lens array 10p shown in the figure, a point light source is configured at the origin on the object plane at the position indicated by A in the figure. The point light source is configured at the origin O, and emits light of a wavelength of 570nm with no intensity difference based on the angle, and performs tracing calculations on 7380 rays. This is also the same in subsequent optical calculations using point light sources. In the process of adjusting the distance between the object plane OP and the imaging plane IP, the L shown in formula (4) of the erect equal-magnification system of the rod lens array is obtained. 0 and L 1 , and configure an object plane OP, a rod lens array and an imaging plane IP.

[0116] L 0 =L 1 =-(1 / n 0 )·tan(π·Z / PP) Formula (4)

[0117] In this way, with L 0 and L 1The regular configuration is obtained together, and the conjugate point on the imaging plane IP of the origin on the object plane OP at this time is set as the image point IQ. The adjustment of the resolution on the image plane calculated in the simulation and the setting of the conditions for achieving the highest resolution are performed as follows. First, together with the object plane OP and the imaging plane IP, the rod lens array 10p shown in the parameters of Table 1 is combined with the L calculated by formula (4). 0 and L 1 On the basis of providing together, the spot diagram of the image on the imaging plane IP is obtained. Next, in the imaging plane IP, the distance from the image point IQ, that is, the lateral light aberration is calculated for each light ray. Then, as an evaluation index of the image, the root mean square (rms) value of the light aberration is calculated as rms A , so that the rms A The high-order coefficients of the rod lens array 10P are optimized in such a way that the value is minimized. This is synonymous with the spherical aberration on the correction axis. The high-order coefficients of the rod lens array 10P refer to the coefficients h when the refractive index distribution n(r) of the rod lenses is expressed by the following equation (5): 4 、h 6 .

[0118] n 2 (r) = n 0 2 ·{1-(g·r) 2 +h 4 (g·r) 4 +h 6 (g·r) 6 Formula (5)

[0119] Next, with respect to the object plane OP at the position indicated by B in the figure, an object plane is prepared when the object plane OP at the position indicated by A in the figure is shifted by -1 [mm] in the z direction together with the point light source. At this time, the distance between the rod lens and the object plane is L 0 +1[mm]. In the case of such an optical system configuration that shifts the object plane OP, the point diagram of the image on the imaging plane IP is obtained in the same manner, and the distance from the image point IQ, that is, the lateral light aberration is calculated for each light ray on the imaging plane IP as an image evaluation index, and the root mean square (rms) value of the light aberration is calculated as rms B Position B corresponds to, for example, a state in which a manuscript or workpiece that should be at position A is so-called "floating" in a direction away from the rod lens array or the image sensor including the rod lens array. In addition, in an optical system including an object plane OP shown in position B obtained by a position shift represented by A from a regular configuration, a so-called defocusing shift of the imaging plane IP is not performed to reduce the increased rms value (improve imaging performance, focusing).

[0120] In the simulation based on the conditions described above, at position A, rms A is 0.0041[mm]. In contrast, the rms at position B is B When the object plane OP shifts from position A, which is a normal configuration, to position B, the rms value of the light aberration increases, resulting in a decrease in imaging performance. In addition, with the shift to position B, compensation or defocusing (position adjustment of the imaging plane IP) for the purpose of improving the rms value of the image on the imaging plane IP is not performed. The rms at position A is A Relative to the rms at position B B RMS r It is 0.040. It is understood that in an optical system including a rod lens array, when there is "floating" (shift in the -z direction) of a workpiece or document, the imaging performance is degraded to this extent.

[0121] exist Fig. 10C and Fig. 10D In the image evaluation of the optical system shown in Table 1, first, the regular position is obtained for the optical system composed of the rod lens array 10p shown in Table 1, and compared with the above-mentioned Fig. 10A and Fig. 10B The rms value of the imaging surface IP relative to the object surface OP shifted by -1 [mm] in the z direction from the position is obtained in the same manner as described above. B The actual calculated value is the same as the rms B =0.1014 [mm]. Next, the rod lens array 10p and each transparent dielectric array 20p shown in Table 2 are combined to form an optical device, and the object plane OP at the position represented by A, the optical device composed of the rod lens array 10p and the transparent dielectric array 20p, and the imaging plane IP are properly arranged in the system. At this time, the distance L between the end face of the rod lens array 10P on the object plane OP side and the object plane OP is 01 For L 0 The object plane OP at the position shown in B in the figure is the object plane OP at the position shown in A in the figure, which is offset by -1 [mm] along the z direction together with the point light source. At this time, the distance between the rod lens and the object plane is L 01 +1[mm]. In the subsequent calculations and evaluations, in addition to the configuration of the optical system in which the object plane OP is offset in the -z direction, the point light source is also offset in the direction parallel to the x-axis (x direction) by 0 times, 0.25 times, 0.50 times, and 0.75 times the diameter of each transparent dielectric (0 mm, 0.25×D 1 mm, 0.5×D 1 mm and 0.75×D 1 mm, D1 is the diameter of the transparent dielectric), and offsets of 0 mm, 0.1 mm, and 0.2 mm are performed in a direction parallel to the y-axis (y direction). Relative to each transparent dielectric array 20p of (i) to (v), 12 point light sources are offset in the x-axis direction and the y-axis direction to obtain the point diagram of each image on the imaging plane IP. The number of point diagrams obtained reaches 5×12=60. For the obtained point diagram, on the imaging plane IP, the distance from the image point IQ, that is, the lateral light aberration, is calculated for each light ray as an evaluation index of the image, and the root mean square (rms) value of the light aberration is calculated as the rms at position B. (k) (m×p) About RMS (k) (m×p) , k is 0.4, 0.6, 0.8, 0.9 and 1.0, which is the P of the transparent dielectric arrays (i) to (v) shown in Table 2 1 / P 0 The corresponding suffixes, m, are 0, 0.25, 0.50, and 0.75, which are the suffixes of the coefficients that determine the offset in the x direction, and p, 0, 0.1, and 0.2, which are the suffixes that determine the offset in the y direction. Then, the rms is finally calculated. (k) (m×p) Relative to the previous rms B The ratio is rms r (k) (m×p) (The properties of the suffixes k, m, and P are the same as above.) In addition to the so-called "floating" state in which the manuscript moves from the height where the manuscript should be located in the direction away from the optical system or the image sensor including the optical system (-z direction), such calculation also takes into account the state in which the object point on the manuscript is offset in the plane perpendicular to the z direction. In addition, in the study of the optical system including the position B that causes the object plane to be offset from the regular position A, the defocusing offset of the imaging plane IP is not performed in the same manner.

[0122] Fig.11 is a ratio showing the rms of the ray aberration in the optical system composed of the rod lens array 10p and the transparent dielectric array 20p. r (k) (m×p) With P 1 / P 0 The relationship between Fig.11 In, with each P 1 / P 0 The corresponding white circles are plotted at a P 1 / P 0 The rms calculated using 12 offset patterns r (k)(m×p) In addition, each P 1 / P 0 The error bars at the same P 1 / P 0 The ratio of the 12 offset patterns is rms r (k) (m×p) The size of the error bar indicates the maximum and minimum values ​​of each P 1 / P 0 RMS r (k) (m×p) gear. Fig. 10C and Fig. 10D The optical system shown has a rms ratio r (k) (m×p) In each P 1 / P 0 The average value is in the range of 0.4 to 0.45. This value is similar to the rms of the optical system including the rod lens array 10p and not including the transparent dielectric array 20p. r Therefore, it can be understood that even if the object plane OP represented by the position A belonging to the regular configuration is shifted in the x direction and the y direction in addition to the shift in the -z direction, the degradation of the optical performance is small in the optical system including the rod lens array 10p and the transparent dielectric array 20p.

[0123] In more detail, if we look at the maximum value of the error bar, then P 1 / P 0 The ratio rms of the case of 0.9 and 1 r (k) (m×p) The maximum value of (k = 0.9 ~ 1.0) is P 1 / P 0 When the ratio is 0.8 or less, the rms rr (k) (m×p) Therefore, although it can be understood that the optical system including the transparent dielectric array has an effect of increasing the depth of field as a whole, 1 / P 0 In an optical system in which a rod lens array and a transparent dielectric array are arranged at a pitch of 0.9 or more, the reduction in resolution cannot be fully compensated by the offset in the x-direction and the y-direction, and as a result, the depth of field may be reduced. Therefore, even when the offset in the x-direction and the y-direction occurs, in order to achieve a larger depth of field, it is preferable that the arrangement pitch P of the transparent dielectric in the transparent dielectric array be 0.9 or more. 1is the arrangement pitch P of the rod lens array 0 Less than 0.8 times (P 1 / P 0 ≦0.8). In addition, it is preferred that the arrangement pitch P of the transparent dielectric in the transparent dielectric array is 1 is the arrangement pitch P of the rod lens array 0 More than 0.3 times (0.3 ≦ P 1 / P 0 ). 1 0.3×P 0 In the above case, it is easy to prevent the light amount from decreasing or the lens opening from being divided, and it is possible to prevent the NA in the sub-scanning direction (y direction) from decreasing and the spot diameter from increasing, or to prevent side peaks from being generated in the scanning direction (x direction) due to the periodic structure of the transparent dielectric array.

[0124] The optical device composed of the rod lens array 10p and the transparent dielectric array 20p was further evaluated. The rod lens array α, β or γ having the optical performance shown in Table 3 was used instead of the rod lens array 10p having the optical performance shown in Table 1, and the transparent dielectric array composed of the group a, group b and group c having the performance and specifications shown in Tables 4 to 12 was used. Table 4 shows the specifications and conditions of an optical device consisting of a combination of a rod lens array α and a transparent dielectric array group a, Table 5 shows the specifications and conditions of an optical device consisting of a combination of a rod lens array α and a transparent dielectric array group b, Table 6 shows the specifications and conditions of an optical device consisting of a combination of a rod lens array α and a transparent dielectric array group c, Table 7 shows the specifications and conditions of an optical device consisting of a combination of a rod lens array β and a transparent dielectric array group a, Table 8 shows the specifications and conditions of an optical device consisting of a combination of a rod lens array β and a transparent dielectric array group b, Table 9 shows the specifications and conditions of an optical device consisting of a combination of a rod lens array β and a transparent dielectric array group c, Table 10 shows the specifications and conditions of an optical device consisting of a combination of a rod lens array γ and a transparent dielectric array group a, Table 11 shows the specifications and conditions of an optical device consisting of a combination of a rod lens array γ and a transparent dielectric array group b, and Table 12 shows the specifications and conditions of an optical device consisting of a combination of a rod lens array γ and a transparent dielectric array group c.

[0125] First, regarding the rod lens arrays of α, β, and γ shown in Table 3, Fig. 10A and Fig. 10B and the method similar to the method described using these drawings to obtain the regular arrangement and the distance L between the rod lens array and the object plane OP in the regular arrangement. 0, the spot diagram on the imaging surface IP when the object surface OP and the point light source are offset by 1 [mm] in the -z direction, and the calculated value based on the spot diagram (h) rms B Value. (h) rms B In the figure, h is α, β or γ, which is a suffix that identifies the rod lens array shown in Table 3. The regular configuration refers to a configuration in which the distance between the object plane OP and the rod lens array, and the distance between the rod lens array and the imaging plane IP are adjusted in such a way that an erect equal-magnification image of an object point on the object plane OP is formed on the imaging plane IP with the highest resolution.

[0126] Next, in Table 4, consider an optical device composed of a combination of a rod lens array α and a transparent dielectric array group a. In the transparent dielectric array group a, P 1 / P 0 =0.4, H is 1.920 ~ 38.400mm. A transparent dielectric array (H = 0.192mm, H / (n 1 ·L 01 )=0.032) are combined to form an optical device consisting of a rod lens array and a transparent dielectric array.

[0127] use Fig. 10C and Fig. 10D and obtaining the regular arrangement and the distance between the rod lens array and the object plane OP in the regular arrangement by the same method as that described using these drawings. (h) L 01 (k) (s) , the spot diagram on the imaging surface IP when the object surface OP and the point light source are offset by 1 [mm] in the -z direction, and the calculated value based on the spot diagram (h) rms B (k) (s) Then, find (h) rms B (k) (s) Compared with the previous (h) rms B than (h) rms r (k) (s) .exist (h) L 01 (k) (s) , (h) rms B (k) (s) as well as(h) rms r (k) (s) In the table, the meanings of the suffixes are as follows. h is α, β or γ, which is the suffix that determines the rod lens array shown in Table 3, and is α in Table 4. k is 0.4, 0.6 or 0.8, which is the suffix that determines P 1 / P 0 The suffix of is 0.4 in Table 4. s is a value in the range of 0.032 to 0.637, which is used to determine H / (n 1 ·L 01 ), which is 0.032 here.

[0128] Similarly, referring to Table 4, an optical device consisting of a rod lens array α and other transparent dielectric arrays belonging to the transparent dielectric array a group is constructed, and the optical devices of each optical device are obtained. (h) rms r (k) (s) h is α, k is 0.4, and s is a value in the range of 0.064 to 0.637, which is used to determine H / (n 1 ·L 01 ) suffix.

[0129] Furthermore, referring to Table 5, an optical device consisting of a rod lens array α and a transparent dielectric array belonging to the transparent dielectric array b group is constructed, and the optical devices are calculated. (h) rms r (k) (s) h is α, k is 0.6, and s is a value in the range of 0.095 to 0.764, which is used to determine the 6 levels of H / (n 1 ·L 01 ) suffix.

[0130] Furthermore, referring to Table 6, an optical device consisting of a rod lens array α and a transparent dielectric array belonging to a transparent dielectric array group c is constructed, and the optical devices are calculated. (h) rms r (k) (s) h is α, k is 0.8, and s is a value in the range of 0.127 to 0.764, which is used to determine the five levels of H / (n 1 ·L 01 ) suffix.

[0131] Thus, an rms index indicating an imaging state when a shift in the -z direction is applied to the object plane is calculated for the optical device composed of a combination of the rod lens array α and the transparent dielectric arrays belonging to the group of transparent dielectric arrays a to c.

[0132] Similarly, referring to Tables 7 to 9, the rms index indicating the imaging state when a -z direction offset is applied to the object plane is obtained for the optical device composed of the combination of the rod lens array β and the transparent dielectric array belonging to the group of transparent dielectric arrays a to c. (h) rms r (k) (s) h is α, β or γ, which is the suffix that determines the rod lens array shown in Table 3, and is β here. k is 0.4, 0.6 and 0.8, which is the suffix that determines P 1 / P 0 The suffix s is used to determine H / (n 1 ·L 01 ) suffix.

[0133] Similarly, referring to Tables 10 to 12, the rms index indicating the imaging state when a -z direction offset is applied to the object plane is obtained for the optical device composed of the combination of the rod lens array γ and the transparent dielectric array belonging to the group of transparent dielectric arrays a to c. (h) rms r (k) (s) h is α, β or γ, which is the suffix that determines the rod lens array shown in Table 3, and is γ here. k is 0.4, 0.6 or 0.8, which is the suffix that determines P 1 / P 0 The suffix s is used to determine H / (n 1 ·L 01 ) suffix.

[0134]

Table 3

[0135]

[0136]

Table 4

[0137]

[0138]

Table 5

[0139]

[0140]

Table 6

[0141]

[0142]

Table 7

[0143]

[0144]

Table 8

[0145]

[0146]

Table 9

[0147]

[0148]

Table 10

[0149]

[0150]

Table 11

[0151]

[0152]

Table 12

[0153]

[0154] Fig. 12A The rms ratio of the light aberration in the optical system composed of the rod lens array α and the transparent dielectric array belonging to the group of the transparent dielectric arrays a to c is shown in FIG. (h) rms r (k) (s) (The meanings of the suffixes h, k, and s are the same as above. They are omitted below) and H / (n 1 ·L 01 )’s relationship curve. Fig. 12B is a graph showing the rms ratio of light aberration in an optical system composed of the rod lens array β and the transparent dielectric array belonging to the group of the transparent dielectric arrays a to c described above. (h) rms r (k) (s) and H / (n 1 ·L 01 )’s relationship curve. Fig. 12C The rms ratio of the light aberration in the optical system composed of the rod lens array γ and the transparent dielectric array belonging to the group of the transparent dielectric arrays a to c is shown in FIG. (h) rms r (k) (s) and H / (n 1 ·L 01 ). Fig. 10C As shown, L 01 is the distance in the z direction between the rod lens array and the object plane OP when the object plane OP and the imaging plane IP become an erect equal magnification system at position A. Table 13 shows the distance in the z direction between the rod lens array and the object plane OP. Figures 12A to 12C Observed, compared (h) rms r (k) (s) H / (n 1 ·L 01) value H / (n 1 ·L 01 ) th In addition, Fig.13 In the example, the P of each optical system is 1 / P 0 The value and ratio (h) rms r (k) (s) H / (n 1 ·L 01 ) th The relationship between the values ​​of and is shown together with the approximate straight line drawn with a dotted line. This relationship indicates that regardless of the type of lens, (H / (n 1 ·L 01 ) th With P 1 / P 0 That is, according to Fig.11 The P shown 1 / P 0 The value and ratio (h) rms r (k) (s) H / (n 1 ·L 01 ) th The relationship between the values ​​of can be understood as follows: in order to further improve the depth of field in an optical device having a lens array and a transparent dielectric array, it is beneficial for the condition of the following formula (6) to be satisfied.

[0155] H / (n 1 ·L 01 )>0.27(P 1 / P 0 )+0.023 Formula (6)

[0156]

Table 13

[0157]

[0158] As described above, a composite image is formed on an imaging surface by overlapping images of single lenses based on the vicinity of adjacent single lenses in a lens array. The imaging based on the single lenses has a light quantity distribution according to the fourth power cosine law, etc., so periodic illumination unevenness may also occur in the composite image. The illumination unevenness can also be corrected by performing gain correction on the image signal from the image sensor, etc. However, when the illumination unevenness exceeds a large value, such as 0.5 of the average illumination, as a practical problem, it may cause a significant reduction in the contrast of the read image of the subject and cause damage such as stripes.

[0159] Therefore, an optical simulation was performed to calculate the irradiance on the imaging surface in an optical device or optical system having a rod lens array and a transparent dielectric array. The illumination analysis software Trace Pro Standard 7 from Lambda Research Corporation in the United States was used to calculate the irradiance. As the conditions for the optical simulation, Fig. 10C and Fig. 10D The optical system shown. As the rod lens array, the rod lens arrays α, β and γ shown in Table 3 are used, and as the transparent dielectric array, the transparent dielectric arrays of the three groups of a', b' and c' shown in Tables 14 to 22 are used. They are combined to form an optical system. In addition, in the optical simulation, the configuration of the object plane, the rod lens array, the transparent dielectric array and the imaging plane is determined in such a way that it becomes an erect equal magnification system and the resolution of the image is the highest. The position of the object plane at this time is set to A. Position A is a regular configuration.

[0160]

Table 14

[0161]

[0162]

Table 15

[0163]

[0164]

Table 16

[0165]

[0166]

Table 17

[0167]

[0168]

Table 18

[0169]

[0170]

Table 19

[0171]

[0172]

Table 20

[0173]

[0174]

Table 21

[0175]

[0176]

Table 22

[0177]

[0178] In the optical simulation, a surface light source is configured to emit uniform light from the object surface at position A, and the uneven illumination in the imaging surface of each optical system is obtained. As a condition for emitting light of a wavelength of 570nm with Lambert's light distribution, the surface light source used in the optical simulation traces 10 million rays. Due to the periodicity of the rod lens array and the transparent dielectric array, the irradiance also tends to be periodic with respect to the main scanning direction (x direction). In applications such as image sensors, the irradiance detected by the photosensitive element array is preferably constant in the main scanning direction. In the case where the irradiance has deviations and periodic changes in the main scanning direction, the image sensor obtains an image with deviations and changes in shades and brightness, which cannot be said to be appropriate. Therefore, in each optical system, a simulation is implemented to obtain the irradiance distribution in the main scanning direction and evaluate the uneven irradiance.

[0179] Fig.14 The results are shown in the case of combining three types of rod lens arrays, α, β and γ, with the transparent dielectric array (P 1 =0.4×P 0 ), b' group of transparent dielectric arrays (P 1 =0.6×P 0 ) and c' group of transparent dielectric arrays (P 1 =0.8×P 0 ) in the optical system, the irradiance unevenness ΔI is obtained in the range of x=0[mm] to x=100[mm]. Fig.14 The horizontal axis is H / (n 1 ·L 01 D), the vertical axis is the irradiance unevenness ΔI. The irradiance unevenness ΔI is obtained by finding the maximum value I of the irradiance within the above range in the main scanning direction (x direction). max and the minimum value of irradiance I min , calculated using the following formula (7).

[0180] ΔI=2×(I max -I min ) / (I max +I min ) Formula (7)

[0181] Fig.14 The relationship between the irradiance unevenness ΔI and the parameter H / (n 1 ·L 01 ). Fig.14 As shown in the figure, the smaller the value of the irradiance unevenness ΔI is, the better. However, when the irradiance unevenness ΔI is proportional to H / (n 1 ·L 01) shows that ΔI has a band-like width regardless of the type of lens and increases with H / (n 1 ·L 01 ) increases. It is speculated that if H / (n 1 ·L 01 ) is larger, the effect of limiting the opening of the rod lens is enhanced, and the angle of light radiated from the transparent dielectric array toward the imaging surface also becomes smaller, and the overlap of the radiation illumination distribution of each transparent dielectric in the transparent dielectric array is reduced.

[0182] In addition, according to Fig.14 The relationship shown is inferred as follows: if H / (n 1 ·L 01 ) is greater than 0.6, the irradiance unevenness ΔI in the optical system combining the rod lens array and the transparent dielectric array will exceed 0.5 depending on the combination of the rod lens and the transparent dielectric array. Based on the results of this study, it can be understood that in order to reduce the irradiance unevenness in an optical device or optical system having a rod lens array and a transparent dielectric array, it is preferable to satisfy H / (n 1 ·L 01 )≦0.6 or less. Furthermore, in H / (n 1 ·L 01 ) is 0.46 or less, and the irradiance unevenness ΔI is 0.3 or less, which is more preferable.

[0183] In the optical device 1a, the irradiance unevenness ΔI is, for example, 0.5 or less. The irradiance unevenness ΔI is preferably 0.4 or less, and more preferably 0.3 or less.

[0184] In the optical device 1a, there may be an air or vacuum layer between the lens array 10 and the transparent dielectric array 20. A transparent adhesive may be filled between the lens array 10 and the transparent dielectric array 20, or there may be a transparent adhesive layer or a resin such as an adhesive layer such as Optical Clear Adhesive (OCA). In the case where there is a resin between the lens array 10 and the transparent dielectric array 20, it is preferred that the refractive index of the resin is close to the refractive index of the lens 11 of the lens array 10 and the refractive index of the transparent dielectric 21 of the transparent dielectric array 20. This is because the loss of light caused by interface reflection can be reduced.

[0185] The use of the optical device 1a is not limited to a specific use. The optical device 1a can be used for optical products or optical equipment such as image sensors, scanners, printers, line sensor cameras, copiers, fax machines, multi-function devices (such as devices including functions such as copiers and printers), appearance inspection devices, and endoscopes.

[0186] Fig.15A FIG. 1 is a diagram showing an example of an image sensor. Fig.15A As shown, the image sensor 3a has an optical device 1a. The image sensor 3a is, for example, a CIS (Contact Image Sensor). In the image sensor 3a, the optical axis of the lens 11 of the lens array 10 of the optical device 1a and the central axis of the transparent dielectric 21 of the transparent dielectric array 20 extend in the z-axis direction. The plurality of lenses 11 in the lens array 10 are arranged in the x-axis direction (main scanning direction). In addition, the size of the image sensor 3a or the accessories included in the image sensor 3a in the x-axis direction may also be larger than their size in the y-axis direction perpendicular to the x-axis and the z-axis.

[0187] like Fig.15A As shown, the image sensor 3a has a housing 30, a linear lighting device 31, a manuscript stage 32, a light receiving element array 33, and a circuit board 34. The optical device 1a, the linear lighting device 31, the light receiving element array 33, and the circuit board 34 are arranged inside the housing 30. The manuscript stage 32 is composed of a glass plate and is arranged in a manner to cover the opening of the housing 30. The linear lighting device 31 emits, for example, substantially uniform illumination light in the x-axis direction to illuminate an object S such as a manuscript. A portion of the illumination light reflected by the surface of the object S passes through the lens array 10 and the transparent dielectric array 20 in sequence and reaches each light receiving element such as a PD or an avalanche photodiode (APD) of the light receiving element array 33, and the information on the surface of the object S is imaged on the light receiving surface of the light receiving element. In the image sensor 3a, the optical device 1a is manufactured in such a manner that the surface of the object corresponds to the object plane OP and the light receiving surface of the light receiving element corresponds to the image plane IP, and an erect equal magnification system is arranged in the optical device 1a. The image sensor 3 a acquires two-dimensional information of the object S by scanning itself in the y-axis direction.

[0188] In the image sensor 3a, the transparent dielectric array 20 is arranged on the light emitting surface side of the lens array 10. With respect to the structure inside the housing 30, the lens array 10 and the transparent dielectric array 20 may be assembled separately, or the lens array 10 and the transparent dielectric array 20 may be integrated in advance by bonding or the like and then assembled to the housing 30. Therefore, the optical device 1a may be configured such that the lens array 10 and the transparent dielectric array 20 are assembled separately, or a structure in which the lens array 10 and the transparent dielectric array 20 are integrated may be adopted.

[0189] Fig. 15B Another example of an image sensor is shown. Fig. 15C Another example of an image sensor is shown. Fig. 15B The image sensor 3b and Fig. 15CThe image sensor 3c shown is constructed similarly to the image sensor 3a except for the parts specifically described. The components of the image sensors 3b and 3c that are the same as or correspond to the components of the image sensor 3a are marked with the same reference numerals, and detailed descriptions are omitted. The description of the image sensor 3a is also applicable to the image sensors 3b and 3c as long as there is no technical contradiction.

[0190] like Fig. 15B As shown, in the image sensor 3 b , the transparent dielectric array 20 is arranged on the light incident surface side of the lens array 10 .

[0191] like Fig. 15C As shown, in the image sensor 3 c , the transparent dielectric array 20 is arranged not only on the light emitting surface side of the lens array 10 , but also on the light incident surface side.

Claims

1. An optical device comprising: A lens array comprising a plurality of lenses arranged in such a manner that optical axes of the plurality of lenses are substantially parallel to each other; and A transparent dielectric array comprises a plurality of transparent dielectrics, wherein the plurality of transparent dielectrics are arranged in such a manner that the central axes of the plurality of transparent dielectrics are substantially parallel to each other. The lens array and the transparent dielectric array are arranged so that the optical axis and the central axis are substantially parallel and an end surface of the lens array faces an end surface of the transparent dielectric array.

2. The optical device according to claim 1, wherein: The lens is a rod lens having a refractive index distribution along a radial direction.

3. The optical device according to claim 1 or 2, wherein: The arrangement pitch P0 of the lens array and the arrangement pitch P1 of the transparent dielectric array satisfy a first condition of 0.3×P0≦P1≦0.8×P0.

4. The optical device according to claim 3, wherein: The refractive index n1 of the transparent dielectric array and the length H [mm] of the transparent dielectric array satisfy H / (n1·L 01 )>0.27×(P1 / P0)+0.023, In the second condition, L 01 It is the distance [mm] between the lens array and the object plane when an erect equal-magnification image of the object plane is formed with the highest resolution.

5. The optical device according to any one of claims 1 to 4, wherein: The irradiance unevenness ΔI is less than 0.5, The irradiance unevenness ΔI has ΔI=2×(I max -I min ) / (I max +I min ), In the relationship described, I max is the maximum value of the irradiance in the main scanning direction of the optical device, I min is the minimum value of the irradiance in the main scanning direction of the optical device.

6. The optical device according to any one of claims 1 to 5, wherein: The refractive index n1 of the transparent dielectric array and the length H [mm] of the transparent dielectric array satisfy H / (n1·L 01 )≦0.6, In the third condition, L 01 It is the distance [mm] between the lens array and the object plane when an erect equal-magnification image of the object plane is formed with the highest resolution.

7. The optical device according to claim 2, wherein: The optical axis of the lens of the lens array is substantially consistent with the central axis of the transparent dielectric of the transparent dielectric array. The fourth condition of tanθ0·H / n1>P1 / 2 is satisfied. n1 is the refractive index of the transparent dielectric, H is the length of the transparent dielectric in a direction parallel to the central axis [mm], P1 is the distance between the central axes of adjacent transparent dielectrics in the transparent dielectric array [mm], θ0 is the aperture angle of the rod lens, In use n(r) 2 =n0 2 ·{1-(g·r) 2 } represents the refractive index distribution of the rod lens, θ0 has the relationship of sinθ0=n0·g·r0, r is the distance from the optical axis of the rod lens in the radial direction [mm], n(r) is the refractive index of the rod lens at distance r, n0 is the refractive index of the rod lens on the optical axis, g is the refractive index distribution constant of the rod lens, r0 is the effective radius of the rod lens [mm]. 8 . An image sensor comprising the optical device according to claim 1 .

9. A method for manufacturing an optical device, which is the method for manufacturing an optical device according to claim 1, wherein: The manufacturing method of the optical device includes the following steps: combining the transparent dielectric array and the lens array in such a manner that the central axis of the transparent dielectric is substantially parallel to the optical axis of the lens and the end face of the transparent dielectric array is substantially parallel to the end face of the lens array.

10. The method for manufacturing an optical device according to claim 9, wherein: The manufacturing method of the optical device comprises the following steps: Arranging the plurality of rod-shaped glasses obtained by the down-drawing so that the central axes of the plurality of rod-shaped glasses are substantially parallel; and The transparent dielectric is obtained by forming a pair of faces substantially perpendicular to the central axis of the glass.

Images