JP2010050696A - Image reading device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an image reading device capable of highly accurately assembling and installing an imaging optical system including a rotationally-symmetrical lens and an anamorphic lens to a lens barrel, sufficiently exerting the optical performance of the imaging optical system, and highly accurately reading image information. <P>SOLUTION: The image reading device includes the rotationally-symmetrical lens and the anamorphic lens with at least one surface formed in an anamorphic shape, and comprises: the lens barrel for holding the imaging optical system for forming an image of the original image on a platen; a reading means having a line sensor arranged at the imaging position of the imaging optical system; and a housing for housing the lens barrel and the reading means. The image reading device for reading the image information of the original image by relatively scanning an original image surface and the housing has a positioning member integrally formed with an elastic part for holding the anamorphic lens to the lens barrel by being engaged with a part of the lens barrel to the lens barrel, and the positioning part for holding the imaging optical system in a rotation-regulated manner to an imaging optical system mounting part provided at the lens barrel. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image reading apparatus, and particularly suitable for an image reading apparatus such as an image scanner, a copying machine, and a facsimile machine, which can perform high-precision image reading by fully exhibiting the optical performance of an imaging optical system. Is something.

  Conventionally, various image reading apparatuses for reading image information of a document have been proposed.

  Among these, there is known a carriage type image reading apparatus that integrally scans a document surface by integrally forming a plurality of mirrors, an imaging optical system, a line sensor (reading means), and the like (see Patent Document 1).

  FIG. 6 is a schematic view of a main part of a conventional carriage type image reading apparatus.

  In FIG. 6, reference numeral 102 denotes a platen glass on which a document 101 is placed. A carriage 107 includes an illumination system 103, which will be described later, a plurality of reflecting mirrors 104a, 104b, 104c, 104d, and 104e, an imaging optical system (an image reading lens) 105, and a reading unit 106. is doing. The carriage 107 scans in the sub-scanning direction (A direction) in the figure by a sub-scanning mechanism 108 such as a motor, and reads image information of the document 101.

  The illumination system 103 includes a xenon tube, a motor lamp, an LED array, and the like. Note that an aluminum vapor deposition plate may be used in combination for the illumination system 103. Each of the reflection mirrors 104 a, 104 b, 104 c, 104 d, and 104 e is bent inside the carriage 107 from the document 101. The imaging optical system 105 focuses light from the original 101 on the surface of the reading means 106. The reading means 106 is composed of a line sensor, and has a configuration in which a plurality of light receiving elements are arranged in a main scanning direction which is perpendicular to the paper surface.

  In the above configuration, the carriage 107 needs to be miniaturized in order to miniaturize the image reading apparatus. In order to reduce the size of the carriage 107, for example, it is necessary to increase the number of reflection mirrors or to reflect the light multiple times with one reflection mirror to ensure the optical path length.

  However, these methods have a problem that the structure inside the carriage 107 is complicated, so that the assembly accuracy becomes strict and the manufacture becomes difficult. There is also a problem that the image forming performance deteriorates in proportion to the surface accuracy of the reflecting mirror and the number of reflections, and the image quality of the read image is lowered.

  Therefore, by introducing an anamorphic lens having at least one surface rotationally asymmetric with respect to the optical axis in the imaging optical system, the imaging optical system 105 is widened to reduce the distance between the object images, and the optical path length itself. There is known an image reading apparatus that shortens the length (see Patent Document 2).

  When an anamorphic lens is incorporated in the imaging optical system 105, the imaging performance of the imaging optical system becomes rotationally asymmetric with respect to the optical axis. For this reason, it is necessary to regulate the main scanning direction of the imaging optical system and the arrangement direction of the plurality of light receiving elements of the reading means so as to match with high accuracy.

Conventionally, there has been proposed an image reading apparatus for accurately fixing the imaging optical system in the main scanning direction in which the line sensor of the reading means is arranged (see Patent Documents 3 and 4). These Patent Documents 3 and 4 disclose a configuration in which the positional relationship between the anamorphic lens, the lens barrel, and the image reading device is fixed with high accuracy.
JP-A-3-113396 JP 2000-171705 A JP 2000-307823 A JP 2004-078149 A

  If an anamorphic lens having an anamorphic surface having a rotationally asymmetric shape is used in addition to the rotationally symmetric lens in the imaging optical system, the optical path length can be shortened, and the effect that the entire system can be reduced in size is easily obtained. It is done.

  However, unless the positional relationship between the rotationally symmetric lens and the lens barrel of the anamorphic lens is assembled with high accuracy, each lens is decentered, optical performance is degraded, and image reading accuracy is degraded. For example, when the anamorphic lens is tilted in the sub-scanning direction, a large amount of decentration aberration occurs, and the image quality of the read image is greatly deteriorated.

  In general, the rotationally symmetric lens can be easily adjusted to the best position by adjusting the rotation within the lens barrel.

  However, since the anamorphic lens includes a rotationally asymmetric surface, it cannot be rotationally adjusted in the lens barrel.

  A method for adjusting the position of the anamorphic lens by applying an external force to the lens barrel by positioning means is known, but this method may cause the lens surface to be distorted by the external force.

  In order to read image information with high accuracy (with high image quality) using an imaging optical system including an anamorphic lens, it is important to position and mount the anamorphic lens on the lens barrel with high accuracy.

  In the present invention, an imaging optical system including an anamorphic lens in addition to a rotationally symmetric lens can be assembled and mounted on a lens barrel with high accuracy, and the optical performance of the imaging optical system is fully exhibited, and image information is highly accurate. An object of the present invention is to provide an image reading apparatus that can be read easily.

The image reading apparatus of the present invention includes an original platen on which an original is placed, a rotationally symmetric lens, an anamorphic lens having at least one anamorphic shape, and an imaging optical system for forming an image of the original, and the connection. A lens barrel for holding an image optical system;
A reading means having a line sensor arranged at an imaging position of the imaging optical system;
A housing that houses the barrel and the reading means;
In the image reading apparatus that reads the image information of the document by scanning the document surface and the housing relatively in a direction perpendicular to the arrangement direction of the pixels of the line sensor,
The imaging optical system is rotationally restricted by an elastic portion for locking the anamorphic lens to the barrel and holding the anamorphic lens on the barrel, and an imaging optical system mounting portion provided on the barrel. It has the positioning member which integrally molded the positioning part for hold | maintaining.

  According to the present invention, an imaging optical system including another anamorphic lens other than a rotationally symmetric lens can be assembled and mounted on a lens barrel with high accuracy, and the optical performance of the imaging optical system can be sufficiently exhibited, and image information can be displayed. An image reading apparatus capable of reading with high accuracy is obtained.

  Embodiments of the present invention will be described below with reference to the drawings.

  The image reading apparatus of the present invention includes a rotationally symmetric lens and an anamorphic lens having at least one anamorphic shape, and has an imaging optical system that forms an image of a document placed on a document table. The imaging optical system is held by a lens barrel.

  Reading means having a line sensor is arranged at the imaging position of the imaging optical system. The lens barrel and reading means are housed and held in a carriage (casing). At this time, the lens barrel holding the imaging optical system is placed on the imaging optical system mounting portion provided in the housing.

  The document table and the casing are scanned relatively in a direction perpendicular to the pixel arrangement direction of the line sensor to read the image information of the document.

  Rotation is restricted around the optical axis by an elastic portion for elastically holding the anamorphic lens in the lens barrel by locking or pressing a part of the lens barrel, and an imaging optical system mounting portion provided in the housing with the imaging optical system For this reason, a positioning member integrally formed with a positioning portion is used. The elastic portion may elastically hold the imaging optical system having an anamorphic lens in the lens barrel.

  With such a configuration, the anamorphic lens is mounted on the lens barrel with high accuracy without decentration, and high optical performance is obtained.

  FIG. 1 is a schematic view of a main part when the image reading apparatus of the present invention is applied to an image forming apparatus such as an image scanner or a copying machine. FIG. 2 is a schematic view of a main part of the first embodiment when the peripheral portion of the imaging optical system in FIG. 1 is viewed from the reading element (reading means) side. FIG. 3 is a sub-scan sectional view of Embodiment 1 of the imaging optical system and the peripheral portion in FIG.

  In the following description, the main scanning direction is the alignment direction of the pixels of the line sensor, and the sub-scanning direction is the direction perpendicular to the alignment direction of the pixels of the line sensor.

  In the figure, reference numeral 2 denotes an original table glass (original table) on which an original 1 is placed. Reference numeral 7 denotes a carriage (housing) which integrally houses an illumination system 3, which will be described later, a plurality of reflecting mirrors 4a, 4b, 4c, 4d, 4e, an imaging optical system 5, a reading means 6, and the like. The carriage 7 is moved in the sub-scanning direction (arrow C direction) by a sub-scanning mechanism 8 such as a sub-scanning motor.

  The illumination system 3 is composed of, for example, a xenon tube, a halogen lamp, an LED array, or the like. You may comprise the illumination system 3 combining reflectors, such as an aluminum vapor deposition board. The reflection mirrors 4a, 4b, 4c, 4d, and 4e are first, second, third, fourth, and fifth reflection mirrors, respectively, and bend the optical path of the light beam from the document 1 inside the carriage 7.

  The imaging optical system 5 forms an image on the surface of the reading means 6 with a light beam based on the image information of the document 1. The imaging optical system 5 in this embodiment includes a rotationally symmetric lens 9 and a lens 10 (hereinafter referred to as an anamorphic lens) 10 having at least one rectangular shape having an anamorphic shape. Reference numeral 11 denotes a positioning member having an elastic portion 21 that can restrict rotation around the optical axis.

  The reading means 6 is composed of a line sensor (CCD or CMOS), and has a configuration in which a plurality of light receiving elements are arranged in a one-dimensional direction (main scanning direction).

  In this embodiment, the luminous flux emitted from the illumination system 3 illuminates the document 1 directly or via a reflective shade (not shown). Then, the reflected light from the original 1 is bent in order in the carriage 7 through the first, second, third, fourth, and fifth reflecting mirrors 4a, 4b, 4c, 4d, and 4e. Yes. Then, the image information of the original 1 is imaged on the line sensor surface by the imaging optical system 5.

  Then, the image information of the document 1 is read two-dimensionally by moving the carriage 7 in the sub-scanning direction (arrow C direction) by the sub-scanning motor 8. The read image information is sent to an external device such as a personal computer or a printer through an interface (not shown).

  The imaging optical system 5 in this embodiment holds a rotationally symmetric lens 9 in a lens barrel 12 as shown in FIGS. Further, the rectangular anamorphic lens 10 is pressed and held from the reading means 6 side by an elastic portion 21 provided on a part of the positioning member 11 outside the lens barrel 12.

  Further, the imaging optical system 5 including the anamorphic lens 10 has an imaging optical system in which a positioning portion 22 provided in a part of the positioning member 11 is provided in the carriage 7 on the image reading apparatus side as shown in FIGS. It is held in a state of abutting on the mounting portion 31.

  The rotation around the optical axis is restricted by abutting the positioning portion 22 of the positioning member 11 against the imaging optical system mounting portion 31.

  The positioning member 11, the elastic member 21, and the positioning portion 22 are integrally formed of sheet metal or the like.

  The imaging optical system mounting unit 31 includes a member that is parallel to the arrangement direction (main scanning direction) of the light receiving elements of the line sensor that is the reading unit 6, and is provided on the carriage 7. Therefore, the rotation of the imaging optical system 5 including the anamorphic lens 10 around the optical axis is restricted by abutting the positioning unit 22 on the imaging optical system mounting unit 31, and the light receiving element arrangement direction (main scanning) of the line sensor Can be positioned parallel to the direction).

  When the imaging optical system 5 is fixed to the imaging optical system mounting part 31, the lens barrel 12 is fixed to the imaging optical system mounting part 31 by a separate lens barrel support member 32.

  At this time, the lens barrel 12 is held in a state in which pressure (biasing force) is applied in the direction of arrow D shown in FIG. When this pressure is strong, the imaging optical system 5 is inclined in the sub-scanning direction with the abutting positioning portion 22 as a fulcrum, but in this embodiment, the positioning member 11 has the elastic portion 21. The extra pressure can be absorbed. Accordingly, the posture of the imaging optical system 5 is not tilted and moves in a state parallel to the light receiving element arrangement direction (main scanning direction) of the line sensor, so that it is possible to reduce an attachment error factor.

  The rotationally symmetric lens of the imaging optical system 5 is held in the lens barrel 12. The anamorphic lens has a rectangular outer shape, and is elastically held by the elastic portion 21 of the positioning member 11 outside the lens barrel 12.

  The positioning portion 22 of the positioning member 11 has an R shape (curved surface shape). That is, the cross-sectional shape is an arc. At least one positioning member 11 is provided outside the effective range in the longitudinal direction of the anamorphic lens 10.

  The positioning portion 22 is the positioning member 11 and is provided outside the effective range in the main scanning direction of the anamorphic lens.

  By positioning the positioning portion 22 in an R shape, the positioning accuracy is improved because the positioning portion 22 comes into abutment with a point when it abuts against the imaging optical system mounting portion 31. Further, by providing the positioning portion 22 outside the effective range in the longitudinal direction of the anamorphic lens 10, even when the component accuracy of the positioning member 11 varies or deteriorates, the angle of rotation around the optical axis can be suppressed as small as possible. .

  In this embodiment, the positioning unit 22 is provided at two locations in the main scanning direction across the optical axis.

As shown in FIG. 2, the interval between the two positioning portions is α, and the effective width of the anamorphic lens in the main scanning direction is β. At this time, α ≧ 2β (1)
It is better to set as follows.

  According to this, the lens barrel 12 holding the imaging optical system 5 can be placed on the imaging optical system mounting portion 31 with high accuracy.

In this example,
α = 30 mm β = 12 mm, which sufficiently satisfies the conditional expression (1).

  As described above, according to the present embodiment, it is possible to perform high-precision image reading by sufficiently exhibiting the optical performance of the imaging optical system having at least one anamorphic lens surface.

  FIG. 4 is a schematic view of a main part of the second embodiment when the peripheral portion of the imaging optical system 5 is viewed from the reading element 6 side in FIG. FIG. 5 is a sub-scan sectional view of the imaging optical system 5 and the peripheral portion of the second embodiment shown in FIG.

  This embodiment is different from the first embodiment in that the rectangular anamorphic lens 41 is adhered and held outside the lens barrel 12 with an adhesive. Further, the anamorphic lens 41 is different in that the anamorphic lens 41 is integrally formed with the positioning member 11 having the elastic portion in Embodiment 1 and capable of restricting rotation around the optical axis.

  When the anamorphic lens 41 is formed by plastic molding, an elastic part 42 is formed on the upper edge part outside the effective range, and a positioning part 43 capable of restricting rotation around the optical axis is simultaneously formed on the lower edge part from the same material.

  For this reason, the same effect as that of the first embodiment is obtained by adhering and fixing to the outside of the lens barrel 12 and abutting the positioning portion 43 integrally formed with the anamorphic lens 41 against the imaging optical system mounting portion 31. Further, the lens barrel support member 44 is pressed (locked) to the elastic portion 42 of the upper edge portion, and the imaging optical system 5 including the anamorphic lens 41 is fixed to the imaging optical system mounting portion 31.

  Thereby, the excess pressure component at the time of fixation can be absorbed like Example 1, and the same effect as Example 1 is acquired.

  In addition, in this invention, it is not limited to the said Example, You may introduce | transduce an anamorphic surface into the rotationally symmetric lens 9. FIG.

  As described above, according to the present invention, the imaging optical system includes the rotationally symmetric lens and the lens having at least one anamorphic shape. A lens barrel that holds the imaging optical system is attached to the imaging optical system mounting portion of the image reading device using a positioning member that has an elastic portion and can regulate rotation around the optical axis. As a result, the main scanning direction of the imaging optical system and the arrangement direction of the light receiving elements of the image reading device can be regulated and matched, the cause of the mounting error can be reduced, and the optical performance can be fully exhibited to achieve high accuracy image reading. An image reading apparatus that can perform the above is achieved.

1 is a schematic diagram of the main part of a first embodiment of an image reading apparatus according to the present invention. FIG. 2 is a schematic view of a main part of a peripheral portion of the imaging optical system according to the first embodiment of the present invention viewed from the reading element side. FIG. 2 is a sub-scan sectional view of the imaging optical system and the peripheral portion according to the first embodiment of the present invention. Schematic view of the essential parts of the periphery of the imaging optical system of Example 2 of the present invention as viewed from the reading element side. FIG. 6 is a sub-scanning sectional view of the imaging optical system and the peripheral portion according to the second embodiment of the present invention. Schematic diagram showing the structure of a conventional image reading apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,101 Document 2,102 Document table glass 3,103 Illumination system 4,104 Reflection mirror 5,105 Imaging optical system 6,106 Reading means 7,107 Carriage 8,108 Sub-scanning mechanism 9 Rotationally symmetric lens 10,41 Anamorphic Lens 11 Positioning member 12 having elastic portion and capable of restricting rotation Lens barrel 21, 42 Elastic portion 22, 43 Positioning portion 31 Imaging optical system mounting portion 32, 44 Lens barrel supporting member

Claims (9)

An image forming optical system that includes an original table on which an original is placed, a rotationally symmetric lens, and an anamorphic lens having at least one surface having an anamorphic shape, and an image forming optical system that forms an image of the original, and a lens barrel that holds the image forming optical system When,
A reading means having a line sensor arranged at an imaging position of the imaging optical system;
A housing that houses the barrel and the reading means;
In the image reading apparatus that reads the image information of the document by scanning the document surface and the housing relatively in a direction perpendicular to the arrangement direction of the pixels of the line sensor,
The imaging optical system is rotationally restricted by an elastic portion for locking the anamorphic lens to the barrel and holding the anamorphic lens on the barrel, and an imaging optical system mounting portion provided on the barrel. An image reading apparatus having a positioning member integrally formed with a positioning portion for holding.   The image reading apparatus according to claim 1, wherein the imaging optical system is restricted from rotating around the optical axis by abutting a positioning portion of the positioning member against the imaging optical system mounting portion.   The rotationally symmetric lens of the imaging optical system is held in the lens barrel, the anamorphic lens has a rectangular shape, and is elastically held outside the lens barrel by the elastic portion of the positioning member. The image reading apparatus according to claim 1 or 2.   The rotationally symmetric lens of the imaging optical system is held in the lens barrel, the anamorphic lens has a rectangular shape, and is bonded and held outside the lens barrel with an adhesive. The image reading apparatus according to claim 1 or 2.   The image reading apparatus according to claim 4, wherein the anamorphic lens is formed integrally with the positioning member.   The image reading apparatus according to claim 1, wherein the positioning portion has an R shape.   The image reading apparatus according to claim 1, wherein at least one positioning unit is provided.   8. The image reading apparatus according to claim 1, wherein the positioning unit is the positioning member and is provided outside an effective range in a main scanning direction of the anamorphic lens. 9. The positioning portions are provided at two locations in the main scanning direction across the optical axis, where α ≧ 2β when the interval between the two positioning portions is α and the effective width of the anamorphic lens in the main scanning direction is β.
The image reading apparatus according to claim 1, wherein the following condition is satisfied.