JP5889684B2 - Erecting equal-magnification lens array unit and image reading apparatus - Google Patents

Description

  The present invention relates to an erecting equal-magnification lens array unit used in an image reading apparatus such as a scanner or a facsimile, and an image reading apparatus using the same.

  A reduction optical system or an erecting equal-magnification optical system is used in an image reading apparatus such as a scanner or a facsimile or an image forming apparatus such as an LED printer. In particular, the erecting equal-magnification optical system has an advantage that the entire apparatus can be easily downsized as compared with the case where the reduction optical system is used.

  In the case of an image reading apparatus, the erecting equal-magnification imaging optical system includes a line-shaped light source, an erecting equal-magnification lens array, and a line image sensor. As an erecting equal-magnification lens array, a pair of positive lenses are arranged such that a transparent flat lens array plate in which a plurality of minute lenses are regularly arranged on one side or both sides is arranged so that the optical axes of the individual lenses coincide with each other. An equal-magnification lens array plate is known. Since such an erecting equal-magnification lens array plate can be formed by a method such as injection molding, it can be manufactured at a relatively low cost, and by combining a plurality of lens array plates in the longitudinal direction, a positive size corresponding to various sizes can be obtained. An equal-magnification lens array can be provided.

  In the erecting equal-magnification lens array plate, there is no wall for isolating the light beam between adjacent lenses, so that the light beam obliquely incident on the erecting equal-magnification lens array plate travels diagonally inside the plate and is adjacent to the lens. There is a problem that so-called crosstalk occurs that enters and exits and reaches a position that is not a predetermined imaging position, which causes flare noise (also referred to as ghost).

  Therefore, various proposals have been made to prevent such crosstalk. For example, the surface of an erecting equal-magnification lens array plate is formed with a light-shielding wall for removing stray light that does not contribute to imaging (Patent Document 1), and a field stop is arranged at an intermediate imaging position (Patent Document) 2) An image processing system using two optical systems (that is, providing two line sensors) (Patent Document 3) is known.

JP 2010-286741 A JP 2009-086627 A JP 2009-246623 A

In order to prevent crosstalk, the method of blocking light by providing walls or dividing the optical system requires high accuracy for parts such as light shielding walls and increases the number of parts, which causes problems in mass productivity and manufacturing cost. There is.
In addition to the problems of the conventional erecting equal-magnification lens array, the present inventor previously proposed an erecting equal-magnification lens array unit having substantial telecentricity to deepen the depth of field (Japanese Patent Application No. 2011-265286). ). In the present invention, it is possible to prevent stray light and crosstalk by skillfully designing the arrangement of the diaphragm for obtaining telecentricity.

  The present inventor aimed to further improve such an erecting equal-magnification lens array having telecentricity, more effectively preventing crosstalk, suppressing the occurrence of flare noise, improving the optical performance, etc. A double lens array unit and an image reading apparatus using the same are provided.

  As a result of intensive studies to solve the above problems, the present inventors have arranged crosstalk by arranging an optical element having a viewing angle adjustment function on the object (original) surface side of the erecting equal-magnification lens array. The present inventors have found a new fact that it can be easily prevented and have completed the present invention.

を満たす、（１）から（２）のいずれかに記載の正立等倍レンズアレイユニット。
（４）第１のレンズの第１面を除く第１のレンズアレイの物体面側には遮光部材が設けられていることを特徴とする（１）から（３）のいずれか記載の正立等倍レンズアレイユニット。
（５）前記遮光部材が遮光マスクであることを特徴とする正立等倍レンズアレイユニット。
（６）前記遮光部材が遮光塗料であることを特徴とする（４）の正立等倍レンズアレイユニット。 That is, the present invention has the following configuration.
(1) a first lens array in which a plurality of first lenses are arranged along a direction perpendicular to the optical axis of the first lens along the incident direction of light from the object surface side to the imaging surface; Between the second lens array in which a plurality of second lenses whose optical axes coincide with each of the first lenses is disposed, and between the first lens and the second lens whose optical axes overlap each other. An erecting equal-magnification lens formed by the first lens, the opening, and the second lens having an optical axis overlapping each other, the light-shielding portion having an opening formed in the vicinity of the second surface of the first lens An erecting equal-magnification lens array unit, characterized in that an optical element having a viewing angle adjustment function is arranged on the object plane side of the first lens array.
(2) The erecting equal-magnification lens array unit according to (1), wherein the optical element having the viewing angle adjustment function is a viewing angle adjustment film.
(3) Each optical system formed by the first lens, the aperture, and the second lens whose optical axes overlap with each other is an erecting equal magnification optical system, and the radius of curvature of the first surface of the first lens is r. ₁ , when the thickness of the first lens is L ₁ and the refractive index of the first lens is n

The erecting equal-magnification lens array unit according to any one of (1) to (2), wherein
(4) The erecting device according to any one of (1) to (3), wherein a light shielding member is provided on the object plane side of the first lens array excluding the first surface of the first lens. 1x lens array unit.
(5) The erecting equal-magnification lens array unit, wherein the light shielding member is a light shielding mask.
(6) The erecting equal-magnification lens array unit according to (4), wherein the light shielding member is a light shielding paint.

  In addition, an image reading apparatus of the present invention includes the erecting equal-magnification lens array unit described in any one of (1) to (6) above.

  Since the erecting equal-magnification lens array unit of the present invention includes an optical element having a viewing angle adjustment function, an incident angle equal to or greater than a predetermined angle of light incident angles is incident on the erecting equal-magnification lens array. Therefore, most crosstalk can be prevented. As a result, the mechanical parts of the erecting equal-magnification lens array unit can be simplified, the mass productivity and the economic efficiency can be improved, and the degree of freedom in arrangement in the optical design can be increased, so that the optical design can be superior. There is an effect.

It is sectional drawing which shows one Embodiment of the erecting equal-magnification lens array unit of this invention. It is the II-II sectional view taken on the line of FIG. FIG. 2 is a cross-sectional view perpendicular to the main scanning direction of FIG. 1, showing an outline of an image reading unit including the erecting equal-magnification lens array unit of FIG. 1. It is a figure which shows the positional relationship of a unit optical system, an image surface, and an object surface. It is a fragmentary sectional view of the unit optical system by the plane perpendicular | vertical to the X direction in FIG. (a), (b) is a figure for demonstrating the change of the image formation position on an image surface when the object surface is displaced from the ideal position in the conventional erecting equal-magnification lens array unit. It is the schematic of the erecting equal-magnification lens array unit used as the comparative example for demonstrating the effect | action of this invention. It is the schematic of the erecting equal-magnification lens array unit based on this invention for demonstrating the effect | action of this invention.

Hereinafter, an embodiment of an erecting equal-magnification lens array unit (hereinafter simply referred to as a lens array unit) of the present invention will be described in detail with reference to the drawings. The lens array unit shown in FIGS. 1 and 2 is provided in an image reading unit of an image scanner (not shown) or the like, and mainly uses an image of an object (an object surface is indicated by A) that is a subject such as a document. It can be read linearly along the scanning direction. By continuously reading a linear image while displacing the image reading unit in the sub-scanning direction perpendicular to the main scanning direction, a two-dimensional image of the subject is read.
In FIG. 1, the sub-scanning direction is a direction perpendicular to the paper surface, and in FIG. 2, the main scanning direction is a direction perpendicular to the paper surface.

  The lens array unit according to the present embodiment includes the first lens array 1, the second lens array 2, and the light shielding unit 3 connecting them as basic components, and further on the object plane A side of the first lens array 1. A viewing angle adjustment film 5 is provided.

  The first lens array 1 is a transparent flat plate in which a plurality of fine first lenses 11 are arranged along the longitudinal direction of the plate (main scanning direction) on one or both sides of the plate. The plurality of first lenses 11 are positioned so that their optical axes are parallel to each other. In addition, the first lens 11 is disposed so as to be in close contact with each other along a direction perpendicular to the optical axis of the first lens 11 (X direction shown in FIG. 1).

  The second lens array 2 is provided with a plurality of second lenses 21 in the same manner as the first lens array 1. The postures of the plurality of second lenses 21 are determined so that the optical axes are parallel to each other.

  The first and second lens arrays 1 and 2 are formed by injection molding or the like. The material of the first and second lens arrays 1 and 2 is preferably a material that can be molded by injection molding or the like, has good light transmittance with respect to light in a necessary wavelength region, and has low water absorption. Cycloolefin resin, olefin resin, polycarbonate and the like can be used.

  The light shielding unit 3 connects the first lens array 1 and the second lens array 2. As shown in FIG. 2, a plurality of light transmitting holes 31 (openings) penetrating from the first lens array 1 toward the second lens array 2 are formed in the light shielding portion 3. The surface on the first lens array 1 side in the light shielding unit 3 shields light incident on a surface other than the light transmitting holes 31. Therefore, the light transmitting hole 22 functions as a field stop means.

A unit optical system 47 (see FIG. 3) is configured by the individual first lens 11, the light transmitting hole 31, and the second lens 21. The first lens 11, the second lens 21, and the aperture position are designed so that each unit optical system 43 is an erecting equal-magnification optical system and substantially telecentric on the object side.
In other words, in order to make the object side of the unit optical system 47 telecentric, it is necessary to match the infinity imaging position by the first lens 11 and the opening position (aperture position) of the light transmission hole 31.
Detailed conditions for becoming substantially telecentric will be described later.

  As shown in FIG. 5, the inner surface of the light transmitting hole 31 is formed in a shape along the side surfaces of two truncated cones having the same center line cl. Further, the aperture of the light transmission hole 31 on the first lens 11 side is formed so as to be smaller than the aperture of the opening on the second lens 21 side. The formation position of the light transmission hole 31 is determined so that the center line cl overlaps with the optical axes of the first lens 11 and the second lens 21.

  Further, the inner surface of the light transmitting hole 31 is subjected to processing for suppressing reflection of light and processing for absorbing light. For example, as a process for suppressing the reflection of light, there are a process called graining for roughening the surface by sandblasting or the like, and a process for suppressing the progress of reflected light by processing the surface into a screw shape. Examples of the light absorbing treatment include application of the inner surface with a light absorbing paint.

  In the lens array unit of the present embodiment, a viewing angle adjustment film 5 (an optical element having a viewing angle adjustment function) is disposed on the object plane A side of the first lens array 1. This viewing angle adjustment film 5 is an optical film having a fine louver structure, and by arranging this film on the object plane A side of the first lens array 1, the visible range of light can be controlled, Specifically, light having a large incident angle can be cut.

  FIG. 3 is a conceptual diagram schematically showing an outline of the image reading unit according to the present embodiment. In FIG. 3, a cover glass 41 is provided. Note that the direction from the back surface to the front surface of the sheet shown in FIG. 3 is the main scanning direction, and the direction from left to right is the sub-scanning direction. Also, the direction from the top to the bottom of FIG. 3 is the optical axis direction.

  The image reading unit 40 includes a cover glass 41, an illumination system 42, an erecting equal-magnification lens array unit 43, an image sensor 44, and a position defining member 45. The cover glass 41, the illumination system 42, the erecting equal-magnification lens array unit 43, and the image sensor 44 are fixed by the position defining member 45 so that their positions and postures are maintained in the state described below.

  A hole 46 is formed in the position defining member 45. The hole 46 has a first chamber r1 and a second chamber r2. The first chamber r1 is formed so as to have a longer width in the sub-scanning direction than the second chamber r2.

  A cover glass 41 is attached to the end of the hole 46 on the first chamber r1 side. An illumination system 42 is disposed in the first chamber r1. In addition, the illumination system 42 is arrange | positioned in the position which does not overlap with the 2nd chamber part r2 seeing from an optical axis direction. The illumination system 42 is provided so that illumination light emitted from the illumination system 42 is emitted in the direction of the cover glass 40. That is, the posture and position of the light source and the illumination optical system constituting the illumination system 42 are determined.

  An erecting equal-magnification lens array unit 43 is inserted into the second chamber r2. In addition, the image sensor 44 is fixed to the end on the second chamber r2 side.

  In addition, the normal line of the plane of the cover glass 41, the optical axis of each optical system provided in the erecting equal-magnification lens array unit 43, and the normal line of the light receiving surface of the image sensor 44 are parallel to the optical axis direction. The posture is adjusted.

  In the configuration as described above, illumination light emitted from the illumination system 42 is irradiated to the subject via the cover glass 41. Reflected light with respect to illumination light from the subject passes through the cover glass 41. The reflected light of the subject forms an image on the light receiving surface of the image sensor 44 by the erecting equal-magnification lens array unit 43. The formed optical image is picked up by the image pickup device 44, and an image signal which is an electric signal is generated.

  The image sensor 44 is a CCD line sensor, a CMOS line sensor, or the like, and generates a one-dimensional image signal. The generated one-dimensional image signal is transmitted to a signal processing circuit and subjected to predetermined image processing. A two-dimensional image signal is generated by generating a one-dimensional image signal of a plurality of frames generated while displacing the image reading unit 40 in the sub-scanning direction.

  The erecting equal-magnification lens array unit 43 includes the first lens array 1, the second lens array 2, and the light shielding unit 3.

  In the present embodiment, the unit optical system 47 is provided with erecting equality by forming both the first surface of the first lens 11 and both surfaces of the second lens 21 to be convex surfaces. Note that the second surface of the first lens 11 may be a convex surface, a concave surface, or a flat surface.

  Furthermore, the first lens 11 is designed and formed to satisfy the following expression (1).

Here, r ₁ is the radius of curvature of the first surface of the first lens 11, L ₁ is the thickness of the first lens 11, and n is the refractive index of the first lens 11.

Further, each unit optical system 47 is designed and formed to satisfy the following expression (2).

Here, y ₀ is the field radius of the unit optical system 47, that is, the radius of the range on the object plane os of light that can be taken in by the unit optical system 47 (see FIG. 4). The distance L ₀ from the unit optical system 47 to the object plane os is determined in advance. The image scanner is formed so that the distance between the glass surface on which the document serving as the subject is placed and the unit optical system 47 is the predetermined distance L ₀ . D is the diameter of the unit optical system 47.

  Further, the inner surface of the light transmitting hole 31 is subjected to processing for suppressing reflection of light and processing for absorbing light. For example, as a process for suppressing the reflection of light, there are a process called graining for roughening the surface by sandblasting or the like, and a process for suppressing the progress of reflected light by processing the surface into a screw shape. Examples of the light absorbing treatment include application of the inner surface with a light absorbing paint.

  According to the erecting equal-magnification lens array unit of the present embodiment configured as described above, the erecting equal-magnification lens array unit that can be formed using a normal lens and has an expanded depth of field as the entire array. Can be formed.

  As shown in FIG. 6A, in the conventional erecting equal-magnification lens array unit 43 ′, the object placed at the position of the ideal object plane os with respect to the distance to the image plane is is the unit optical system. 47 'forms an equal-magnification erect image on the image surface is. An image formed by the plurality of unit optical systems 47 'is projected as one whole image without causing a positional shift.

  However, as shown in FIG. 6 (b), when the object plane os is displaced from the ideal position, the unit magnification in the image plane is of each unit optical system 47 ′ is lost, and the same one-point image plane on the object plane os. The imaging positions at is are different between adjacent unit optical systems 47 '. Therefore, the image projected by the entire erecting equal-magnification lens array unit 43 'is blurred. Therefore, the depth of field of the erecting equal-magnification lens array unit 43 'as a whole becomes shallow.

  In general, as the incident angle of the principal ray on the object side increases, the change in the magnification of the lens with respect to the displacement of the object plane os increases. In the entire erecting equal-magnification lens array unit, the larger the change in magnification, the greater the deviation of the imaging position of the same point on the object plane os by the adjacent lenses.

  Therefore, ideally, if the incident angle of the chief ray is zero, the magnification does not change with respect to the displacement of the object plane os. Therefore, even if the object plane os is displaced from the ideal position, the image is formed at the same position on the image plane is without shifting the imaging position by one point of the separate lens on the object plane os. That is, if the individual optical systems constituting the lens array are object-side telecentric, the depth of field of the entire lens array can be kept deep. As described above, the erecting equal-magnification lens array unit 43 of the present embodiment can increase the subject depth of the entire lens array.

  In the present embodiment, by forming the first lens 11 so as to satisfy the expression (1), the object-side telecentricity is provided in each unit optical system 47 as described below.

  In order to make the object side of the unit optical system 47 telecentric, it is necessary to match the rear focal point of the first lens 11 with the position of the stop. The rear focal position of the first lens 11 is substantially equal to the imaging position of the object at infinity by the first lens 11. Further, the small-diameter portion of the light transmitting hole 31 functions as a stop of the unit optical system 47.

  Therefore, in order to make the object side of the unit optical system 47 telecentric, it is necessary to match the infinity imaging position by the first lens 11 with the position of the small diameter portion of the light transmission hole 31.

  As will be described later, the small-diameter portion of the light transmitting hole 31 is preferably disposed on the second surface of the first lens 11 or in the vicinity of the second surface. Therefore, when the small-diameter portion of the light transmission hole 31 is disposed in the vicinity of the second surface of the first lens 11, the infinite image formation position by the first lens 11 is substantially on the second surface of the first lens 11. Therefore, the unit optical system 23 can be provided with object side telecentricity.

  Conditions for matching the infinitely far imaging position with the second surface of the first lens 11 are determined as follows. As the geometric optical relationship before and after the first surface of the first lens 11, Equation (3) is established from Abbe's invariant.

However, in equation (3), s ₀ is the distance between the object and the first surface of the first lens 11. Further, s ₁ is a distance between the first surface of the first lens 11 and the imaging position of the light emitted from the first surface of the first lens 11.

Since the imaging position of an object at infinity is determined, equation (3) can be transformed into equation (4) when s ₀ is infinite.

When the expression (4) is satisfied, the position at the distance s ₁ from the first surface of the first lens 11 is the infinity imaging position of the first lens 11 whose radius of curvature of the first surface is r _1. Become. Therefore, in order to image an object at infinity of the first lens 11 on the second surface of the first lens 11, it is necessary to satisfy the expression (5).

  However, even if the expression (5) is not satisfied, the second surface of the first lens 11 is connected at infinity if the absolute value of the left side of the expression (5) is not more than an allowable value that can be regarded as substantially zero. It is possible to substantially match the image position. Note that the left side of the equation (5) affects not only the adjustment of the infinity imaging position but also the magnification of the first lens 11. Therefore, the allowable value is determined in consideration of the adjustment of the infinity imaging position and the magnification of the first lens 11.

  As the absolute value of the left side of the equation (5) increases, the infinity imaging position is separated from the second surface of the first lens 11. The farther the infinity imaging position is, the lower the object side telecentricity of the first lens 11 is. If the allowable value is 0.3, the telecentricity on the object side of the first lens 11 is maintained.

  Moreover, the magnification of the first lens 11 increases as the absolute value of the left side of the equation (5) increases. In the present embodiment, the first lens 11 is desirably a reduction optical system, that is, the magnification is less than 1. This is because the unit optical system 47 is configured using the first lens 11 and the second lens 21 so as to have erecting equal magnification.

  The fact that the magnification of the first lens 11 needs to be less than 1 will be described more specifically. Since the magnification of the unit optical system 47 is 1, the product of the magnifications of the first lens 11 and the second lens 21 constituting the unit optical system 47 is 1. Therefore, one of the first lens 11 and the second lens 21 needs to be a reduction optical system, and the other needs to be a magnification optical system. As described above, the first lenses 11 are arranged along the X direction so as to be in close contact with each other (see FIG. 1). Therefore, in order for the first lenses 11 to be in close contact with each other, it is an essential condition that the first lens 11 is a reduction optical system.

  When the absolute value of the left side of the equation (5) is less than 0.2, the magnification of the first lens 11 is less than 1. Therefore, the allowable value considering the magnification of the first lens 11 is calculated to be 0.2.

  Therefore, considering both the use of the infinity imaging position and the magnification of the first lens 11, the allowable value used for the absolute value on the left side of the equation (5) is preferably 0.2. By setting the allowable value to 0.2, the equation (1) is obtained.

  Next, the reason why it is preferable to arrange the small-diameter portion of the light transmitting hole 31 on the second surface of the first lens 11 or in the vicinity of the second surface will be described.

  Between the 1st lens 11 and the 2nd lens 21, the light-shielding wall for stray light prevention from the arbitrary unit optical systems 47 to the other unit optical system 47, and the aperture_diaphragm | restriction for adjusting brightness are provided. It is necessary to provide it. In the present embodiment, the inner wall of the light transmitting hole 31 formed in the light shielding part 3 can function as a light shielding wall. Therefore, the stop is disposed either between the first lens 11 and the light shielding unit 3 or between the light shielding unit 3 and the second lens 21.

  Incidentally, dust may adhere to the second surface of the first lens 11 and the first surface of the second lens 21. When dust adheres, the amount of light of the subject image that reaches the image sensor 44 decreases. In order to reduce the influence of dust as much as possible, the light flux passing through the second surface of the first lens 11 and the first surface of the second lens 21 to which dust can be attached is made as thick as possible. desirable.

  In order to satisfy such a condition, it is necessary to sufficiently separate the imaging position of the optical image of the subject at a finite distance from the second surface of the first lens 11 and the first surface of the second lens 21. There is. In order to sufficiently separate the imaging position of the optical image of the subject at a finite distance from both, it is preferable to form the optical image of the subject at a finite distance inside the light transmission hole 31. In addition, in order to form an optical image of a subject at a finite distance inside the light transmission hole 31, an object at infinity is formed at an arbitrary position on the first lens 11 side from the imaging position. There is a need.

  As described above, in order to provide telecentricity on the object side, it is necessary to arrange a stop at the focal point of the first lens 11. Therefore, it is necessary to dispose the stop closer to the first lens 11 than the inside of the light transmitting hole 31. Therefore, it is necessary to provide a diaphragm between the first lens 11 and the light shielding unit 3.

  Further, in order to prevent stray light from any unit optical system 47 to another unit optical system 47, the light flux incident on the second surface of the first lens 11 and the first surface of the second lens 21 is the first light beam. The diameters of the second lenses 11 and 21 are required to be thinner. In order to reduce the luminous flux on the second surface of the first lens 11 and the first surface of the second lens 21, it is between the second surface of the first lens 11 and the first surface of the second lens 21. It is necessary to shorten the distance.

  Further, the stray light prevention effect becomes higher as the light shielding wall becomes longer along the optical axis direction. Therefore, in order to maximize the stray light prevention effect of the light shielding wall at a short distance between the second surface of the first lens 11 and the first surface of the second lens 21, It is required that the light transmission hole 31 covers the entire optical path between the two lenses 21. That is, it is preferable that one end portion of the light transmitting hole 31 matches the second surface of the first lens 11 and the other end portion matches the first surface of the second lens 21. In other words, it is preferable that the gap is not provided between the light transmitting hole 31 and the first lens 11 and the second lens 21.

  Since no gap is provided between the second surface of the first lens 11 and the light transmission hole 31, it is necessary to closely contact the diaphragm with the end of the light transmission hole 31 on the first lens 11 side. Instead of bringing the diaphragm into close contact with the end of the light transmitting hole 31, it is possible to function as a diaphragm by forming a small diameter portion at the end of the light transmitting hole 31. Therefore, it is preferable that the small-diameter portion of the light transmitting hole 31 is disposed on the second surface of the first lens 11 or in the vicinity of the second surface.

Further, according to the present embodiment, the unit optical system 47 is formed so that 0.5 ≦ y ₀ / D. Therefore, since all the points on the object plane os can be included in the field of view of any of the unit optical systems 47, partial omission of the image is prevented.

By the way, as y ₀ / D increases, the unit optical system 47 also includes the object plane os at a distance from the optical axis in the field of view. Therefore, when y ₀ / D increases, the number of unit optical systems 47 that image one point on the object plane os increases, and the influence of the deviation of images formed by different unit optical systems 47 increases.

Therefore, in the present embodiment, the unit optical system 47 is formed so that y ₀ / D ≦ 1. Therefore, the number of unit optical systems 47 that image one point on the object plane os is limited to 2 or less, and the influence of image shift can be reduced.

  Further, in the present embodiment, in order to block light from the other unit optical system 47 and prevent crosstalk, as shown in FIGS. 1 and 2 on the object plane A side of the first lens array 1. A viewing angle adjusting film 5 (an optical element having a viewing angle adjusting function) is disposed. This viewing angle adjustment film 5 is an optical film having a fine louver structure, and by arranging this film on the object plane A side of the first lens array 1, the visible range of light can be controlled, Specifically, light having a large incident angle can be cut. As the viewing angle adjusting film 5, for example, “3M light control film” (“3M” is a registered trademark) manufactured by Sumitomo 3M Co., Ltd. can be used.

  The viewing angle adjustment film 5 has a tendency that the amount of light transmitted through the viewing angle adjustment film 5 gradually decreases from the maximum incident angle to the viewing angle adjustment angle due to its characteristics. Therefore, it can be appropriately determined in use in relation to the telecentricity of the erecting equal-magnification optical system to be used. For example, in the optical system shown in the examples described later, an effective F value that is an index indicating the substantial brightness of an image is designed as F = 12.2, and a viewing angle adjusting film has a thickness of 0.5 mm and a visible angle of 48. The degree of light reduction in the optical system could be suppressed to 10% or less.

  The viewing angle adjustment film 5 is disposed on the object plane A side of the first lens array 1. At this time, the viewing angle adjustment film 5 may be in contact with the object plane A of the first lens array 1 or may be separated from the object plane A within a range that does not affect the image. This is because the image of the viewing angle adjustment film 5 is formed on the image sensor 44 if it is too far from the object plane A (in other words, close to the original surface). Therefore, it is determined appropriately according to the optical characteristics of the erecting equal-magnification optical system.

  Further, according to the present embodiment, the first lenses 11 are disposed so as to be in close contact with each other along the X direction shown in FIG. With such a configuration, it is possible to form an image having no missing portion along the X direction.

  In the present embodiment, as described above, since each unit optical system 47 is substantially telecentric on the object side, the amount of light transmitted from a point located outside the diameter of the unit optical system 47 is low. Therefore, if there is a gap between the adjacent unit optical systems 47, the image of the point on the object plane os on the extension of the gap becomes extremely dark, and the image may be lost. However, as described above, since the first lens 11 is in close contact along the X direction, it is possible to obtain an image without such a gap and without missing along the X direction.

  Further, in the present embodiment, since the aperture of the light transmission hole 31 on the first lens 11 side is smaller than the aperture on the second lens 21 side, the stray light from the first lens 11 of the other unit optical system 47 is reduced. It is possible to prevent the incident on the second lens 21.

  In the first lenses 11 that are in close contact with each other, stray light may be incident from the side surfaces of the adjacent first lenses 11. Due to the mixing of such stray light, the influence of noise on the image to be formed becomes large. However, as in the present embodiment, stray light is suppressed by suppressing the incidence of stray light to the second lens 21 using the light transmitting holes 31, and the influence of image noise can be reduced. .

  In the present embodiment, the inner surface of the light transmitting hole 31 is subjected to a process for suppressing reflection of light and a process for absorbing light, so that the inner surface of the light transmitting hole 31 passes through the opening on the first lens 11 side. Propagation of incident stray light to the second lens 21 can be prevented.

  Next, the effect | action of this embodiment at the time of using the above viewing angle adjustment films 5 is demonstrated. FIG. 7 shows an erecting equal-magnification lens array unit when the viewing angle adjustment film 5 is not provided, and corresponds to a comparative example of the present embodiment. When light (indicated by an arrow M) having an incident angle α of 24 degrees or more is incident on the lens array unit from the object N, crosstalk occurs and causes flare noise (ghost).

On the other hand, in the erecting equal-magnification lens array unit using the viewing angle adjusting film 5, as shown in FIG. 8, when light having an incident angle α of 24 degrees or more is incident (indicated by an arrow M), Since the light is cut by the angle adjusting film 5 and does not enter the first lens array 1, it is possible to prevent the occurrence of crosstalk. In FIGS. 7 and 8, an arrow M ₀ indicates image light.

  Thus, by using the viewing angle adjusting film 5, light having a relatively large incident angle that causes crosstalk is cut. On the other hand, the field stop by the light shielding unit 3 is effective for crosstalk caused by light having a small incident angle, and the occurrence of crosstalk can be prevented.

Even if the incident angle α is less than 24 degrees, crosstalk may occur when the light is incident on the object plane side of the first lens array 1 excluding the first surface of the first lens 11. . Therefore, it is preferable to form a light-shielding mask (light-shielding member) by coating light-shielding paint on the object surface side of the first lens array 1 excluding the first surface. Further, it is preferable to form a similar light shielding mask on the side surfaces of the first and second lens arrays.
As the light-shielding paint, a black paint for plastics conventionally used for the purpose of shielding light, or a publicly known light-shielding paint such as water-based ink can be used.

  Note that many of the causes of crosstalk are caused by the incidence of light having a large incident angle, and thus there is no need to provide a field stop. In the above-described embodiment, the field stop is provided in the light-shielding portion 3. However, the present invention is not limited to this, and can be provided in any place in the optical system of the lens array unit.

  Next, the effects of the present invention will be described by way of examples. However, the present examples are merely examples for explaining the effects of the present invention, and do not limit the present invention.

  Using the lens data shown in Tables 1 and 2, a unit optical system 23 (F value 12.2) having telecentricity on the object side was designed. The surface corresponding to the surface number in Table 1 is shown in FIG.

However, in Table 1,
* 1 indicates an aspherical surface, and the aspherical expression is given by the following expression (12).
* 2 is SCHOTT AG bk7.
* 3 is ZEON CORPORATION, ZEONEX (registered trademark) E48R.
* 4 is the aperture.

In the above formula,
Z is the depth from the tangent plane to the surface vertex,
r is the radius of curvature,
h is the height from the optical axis,
k is the conic constant,
A is the fourth-order aspheric coefficient,
B is the sixth-order aspheric coefficient,
C is the 8th-order aspheric coefficient,
D is a 10th-order aspheric coefficient.
Table 2 shows the conic constant k and aspheric coefficients A, B, C, and D.

Both the first lens array having the surfaces 3 and 4 in Table 1 and the second lens array having the surfaces 7 and 8 in Table 1 both use resin (ZEONEX manufactured by Nippon Zeon Co., Ltd.). Made by injection molding. Acrylic lacquers are provided on the side surfaces of the first and second lens arrays and the three surfaces in Table 1 constituting the lenses of the first lens array (excluding the first surface of the lens on the object plane side) for light shielding. A light-shielding coating was applied using a black-type black shading paint (Aclick # 1000, manufactured by Kansai Paint Co., Ltd.).
The positions of the first and second lens arrays are regulated according to the design values shown in Table 1, and the viewing angle is further close to the object side lens (surface 3 side in Table 1) of the first lens array. An erecting equal-magnification optical system as shown in FIG.
As a viewing angle adjusting member, a “3M light control film” manufactured by Sumitomo 3M Co., Ltd. was incorporated into a position regulating member provided at a position 0.5 mm away from the three surfaces of the object side lens.

In the erecting equal-magnification lens array unit described in the embodiment using the viewing angle adjusting film 5, as shown in FIG. 8, when light having an incident angle α of 24 degrees or more is incident (shown by an arrow M), Since the light is cut by the angle adjusting film 5 and does not enter the first lens array 1, it is possible to prevent the occurrence of crosstalk. In FIGS. 7 and 8, an arrow M ₀ indicates image light.

  On the other hand, as shown in FIG. 7, in the erecting equal-magnification lens array unit in which the viewing angle adjusting film 5 is removed from the configuration of the above embodiment, the incident angle α is 24 degrees from the image N to the lens array unit. When the above light (indicated by an arrow M) was incident, flare noise (ghost), which was thought to be due to crosstalk, occurred.

  Thus, by using the viewing angle adjusting film 5, light having a relatively large incident angle that causes crosstalk is cut. On the other hand, the field stop by the light shielding unit 3 is effective for crosstalk caused by light having a small incident angle, and the occurrence of crosstalk can be prevented.

DESCRIPTION OF SYMBOLS 1 1st lens array 2 2nd lens array 3 Light-shielding part 5 Viewing angle adjustment film (Optical element with a viewing angle adjustment function)
11 First lens 21 Second lens 31 Translucent hole

Claims (7)

Along the incident direction of light from the object surface side to the imaging surface,
A first lens array in which a plurality of first lenses are arranged along a direction perpendicular to the optical axis of the first lens;
A second lens array in which a plurality of second lenses whose optical axes coincide with each of the first lenses are disposed;
The first lens array 1 penetrates from the first lens array 1 toward the second lens array 2 in the vicinity of the second surface of the first lens between the first lens and the second lens whose optical axes overlap each other. A plurality of light transmitting holes are formed,
An erecting equal-magnification lens array unit formed by the first lens, the translucent hole , and the second lens whose optical axes overlap each other,
The first lens array is a transparent flat plate in which a plurality of first lenses are arranged so that the optical axes are parallel to each other, and the second lens array is such that the optical axes are parallel to each other. Is a transparent flat plate in which a plurality of second lenses are arranged,
The object side of the unit optical system constituted by the first lens, the light transmitting hole and the second lens is substantially telecentric,
An optical element having a viewing angle adjustment function is disposed on the object plane side of the first lens array,
The translucent hole has a small-diameter portion that functions as a diaphragm and is disposed on or near the second surface of the first lens, and the aperture on the first lens side is the second lens side. Smaller than the caliber of
An erecting equal-magnification lens array unit characterized by that.   The erecting equal-magnification lens array unit according to claim 1, wherein the optical element having the viewing angle adjustment function is a viewing angle adjustment film. Each optical system formed by the first lens, the light transmitting hole , and the second lens whose optical axes overlap each other is an erecting equal-magnification optical system,
When the radius of curvature of the first surface of the first lens is r ₁ , the thickness of the first lens is L ₁ , and the refractive index of the first lens is n

The erecting equal-magnification lens array unit according to claim 1 or 2, wherein   The erecting equal-magnification lens array unit according to any one of claims 1 to 3, wherein a light-shielding member is provided on the object plane side of the first lens array excluding the first surface of the first lens. .   5. The erecting equal-magnification lens array unit according to claim 4, wherein the light shielding member is a light shielding mask.   5. The erecting equal-magnification lens array unit according to claim 4, wherein the light shielding member is a light shielding paint.   An image reading apparatus comprising the erecting equal-magnification lens array unit according to claim 1.

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