JP2006250997A - Image reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve reading accuracy in an image reader for reading an original by switching a plurality of lenses. <P>SOLUTION: The image reader is equipped with: a platen; an image sensor; a first lens barrel; a first lens held in the first lens barrel and forming the image of an original positioned on the platen on the image sensor; a lens carriage on which the first lens barrel is mounted in posture that the optical axis of the first lens turns in an optional direction; a lens adjusting part fixing the first lens barrel on the lens carriage in the posture that the optical axis of the first lens turns in the optional direction; a second lens barrel mounted on the lens carriage; a second lens held in the second lens barrel and forming the image of the original positioned on the platen on the image sensor; and a lens switching part switching a first state where the first lens is positioned on an optical path leading to the image sensor from the original and a second state where the second lens is positioned on the optical path by driving the lens carriage. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image reading apparatus, and more particularly to an image reading apparatus including a plurality of lenses for forming an image of a document on an image sensor.

2. Description of the Related Art Conventionally, there has been known an image scanner that includes a plurality of lenses having different resolutions and switches the lenses according to a document type (for example, Patent Document 1).
In order to read the document accurately, the image sensor and the lens must be fixed so that the light receiving surface of the image sensor and the optical axis of each lens are perpendicular to each other. However, according to the image scanner described in Patent Document 1, since there is no mechanism for correcting the variation in the optical axis direction of each lens due to the dimensional tolerance of parts, the manufacturing cost increases due to strict dimensional tolerance management, There is a problem that reading accuracy cannot be obtained.

US Pat. No. 5,577,697

  The present invention has been created in view of the above-described problems, and aims to improve reading accuracy in an image reading apparatus that reads a document by switching a plurality of lenses.

  (1) An image reading apparatus for achieving the above object includes a platen, an image sensor, a first lens barrel, and an original document held by the first lens barrel and positioned on the platen. A first lens for imaging, a lens carriage on which the first lens barrel can be mounted in an orientation in which the optical axis of the first lens is directed in an arbitrary direction, and the optical axis of the first lens in an arbitrary direction A lens adjustment section for fixing the first lens barrel to the lens carriage in a directed orientation, a second lens barrel mounted on the lens carriage, and an original document held by the second lens barrel and positioned on the platen A first lens in which the first lens is positioned on an optical path from the document to the image sensor by driving the lens carriage. And a lens switching portion that switches a second state in which the second lens is positioned in the optical path.

  According to the present invention, since at least one of the two lenses can be fixed to the lens carriage in an attitude in which the optical axis is directed in an arbitrary direction, the two lenses are attached to the lens carriage in an attitude in which the optical axes are parallel to each other. Can be mounted on. Therefore, according to the present invention, it is possible to improve reading accuracy in an image reading apparatus that reads a document by switching a plurality of lenses.

(2) The first lens barrel may be mounted on the lens carriage so as to be reciprocally movable in a direction orthogonal to the light receiving surface of the image sensor. The lens adjustment unit may fix the first lens barrel to the lens carriage at a position at an arbitrary distance from the light receiving surface.
By adjusting the direction of the optical axis of the first lens, the distance from the light receiving surface of the image sensor to the first lens varies. According to the present invention, since the distance from the light receiving surface of the image sensor to the first lens can be adjusted according to the adjustment of the direction of the optical axis of the first lens, the reading accuracy can be further improved.

(3) The first lens barrel may be mounted on the lens carriage so as to reciprocate in a direction parallel to the light receiving surface of the image sensor. The lens adjustment unit may fix the first lens barrel to the lens carriage at an arbitrary position on a plane parallel to the light receiving surface.
The point at which the optical axis intersects the light receiving surface of the image sensor varies by adjusting the direction of the optical axis of the first lens. According to the present invention, since the position of the first lens can be adjusted on a plane parallel to the light receiving surface according to the adjustment of the direction of the optical axis of the first lens, the reading accuracy can be further improved.

Embodiments of the present invention will be described below based on a plurality of examples. In each of the embodiments, the component having the same reference sign corresponds to the component of the other embodiment having the reference sign.
(First Example)
FIG. 2 is a schematic diagram showing the internal structure of the image scanner 1 as the first embodiment of the image reading apparatus according to the present invention. FIG. 3 is a block diagram illustrating a main configuration of hardware of the image scanner 1. The image scanner 1 is a so-called flatbed type that reads a document 34 placed on a document table 32 as a platen described in the claims.
The document table 32 is formed of a transparent plate such as a glass plate, and a document 34 such as a printed document, a photograph, a book, a 35 mm strip film, or a 35 mm mount film is placed on the board surface.

  The main carriage 20 is slidably fitted to a guide rod 30 parallel to the surface of the document table 32. The main carriage 20 includes a first light source 24, a mirror 22, a lens unit 10, and an image sensor 28. The main carriage 20 is pulled by a belt hung on a pulley driven by a main carriage conveyance motor (not shown), and reciprocates in the directions of arrows X and Y in parallel with the surface of the document table 32. When the first light source 24, the mirror 22, the lens unit 10, and the image sensor 28 are conveyed by the main carriage 20 in the directions of arrows X and Y parallel to the surface of the document table 32, the main scanning range for reading the document moves. .

The first light source 24 and the second light source 36 are illumination devices such as a white cold cathode fluorescent lamp. The first light source 24 and the second light source 36 illuminate the document 34 placed on the document table 32.
The lens 12 or 13 (see FIG. 3) mounted on the mirror 22 and the lens unit 10 includes reflected light from the document 34 illuminated by the first light source 24 and transmitted light from the document 34 illuminated by the second light source 36. Is incident on the light receiving surface of the image sensor 28. At this time, the optical axis of either the lens 12 or 13 selected by the CPU 60 is localized on the optical path from the document 34 to the image sensor 28 via the mirror 22. Details of the lens unit 10 will be described later.

  The image sensor 28 is a so-called linear image sensor in which a large number of photoelectric conversion elements (not shown) composed of photodiodes or the like are linearly arranged. The image sensor 28 is mounted on the main carriage 20 so that a large number of photoelectric conversion elements are arranged in parallel with the central axis of the tubular first light source 24. The image sensor 28 is fixed to the main carriage 20 so that the orientation and position of the light receiving surface can be adjusted when attached. Electric charges corresponding to the amount of received light are accumulated in each photoelectric conversion element of the image sensor 28 by photoelectric conversion. The electric charge accumulated in each photoelectric conversion element is transferred to the output unit of the image sensor 28 by a CCD (Charge Coupled Device). This charge transfer may be performed by CMOS (Complementary Metal Oxide Semiconductor). The analog signal output from the image sensor 28 is output to the AFE unit 76 (see FIG. 3).

  The CPU 60 executes a program stored in the ROM 82 and controls each unit of the image scanner 1. The ROM 82 is a non-volatile memory that stores various programs, various data, and the like. These programs and various types of data can be stored in the ROM 82 by downloading from a predetermined server via a network, reading from a computer-readable storage medium such as a removable memory (not shown), and the like. The RAM 74 is a memory that temporarily stores various programs and various data. The RAM controller 72 controls data transfer between the CPU 60, the AFE unit 76, the image processing unit 78, the external interface controller 80, and the like and the RAM 74.

The first light source controller 62 includes an inverter circuit, a control circuit, and the like (not shown), and controls the turning on and off of the first light source 24. The second light source controller 64 includes an inverter circuit, a control circuit, and the like, and controls turning on and off of the second light source 36.
The image sensor controller 70 is a drive circuit that outputs drive pulses necessary for driving the image sensor 28 to the image sensor 28, and includes, for example, a synchronization signal generator, a drive timing generator, and the like.

The main carriage controller 68 includes the above-described main carriage transport motor (not shown), a main carriage transport motor drive circuit, a control circuit, and the like. The main carriage controller 68 receives a main carriage conveyance control signal transmitted from the CPU 60, and controls the rotation direction, rotation speed, and the like of the main carriage conveyance motor.
The lens unit controller 66 includes a drive circuit and a control circuit for the motor 50 that drives the lens unit 10. The lens unit controller 66 receives a lens replacement signal transmitted from the CPU 60 and controls the rotation direction, rotation speed, and rotation angle of the motor 50.

The analog front end (AFE) unit 76 performs CDS (Correlated Double Sampling) processing, optical black clamp control for reproducing the black level of the image, level adjustment processing of the electric signal by adjusting the gain of the electric signal of the image, A scan image digitized by performing quantization processing or the like is stored in the RAM 74 via the RAM controller 72.
The image processing unit 78 is a DSP (Digital Signal Processor) that performs signal processing for performing image processing such as gamma correction and shading correction on the scanned image stored in the RAM 74 in cooperation with the CPU 60.
The external interface controller 80 connects the image scanner 1 and an external system such as a PC (Personal Computer) so that they can communicate with each other.

  FIG. 4 is a perspective view showing the lens unit 10. The lens unit 10 is accommodated in the main carriage 20, and the first lens 12, the first lens barrel 100, the first holder 102, the second lens 13, the second lens barrel 115, the second holder 116, the rack 16, the lens carriage 14, and the like. Is provided. A shaft (not shown) extending in the main scanning direction is inserted into the bearings 111 and 112 of the lens carriage 14. The rack 16 is fixed to the lens carriage 14 and meshes with a spur gear 46 that is rotatably supported by the main carriage 20. When the motor 50 is driven, the spur gear 46 is driven by a drive transmission mechanism 52 such as a worm or worm wheel connected to the motor 50, and the lens unit 10 is parallel to the document table 32 along the shaft in the main carriage 20. To move. The motor 50 and the drive transmission mechanism 52 correspond to the lens switching unit described in the claims. In this embodiment, the lens carriage 14 is slidably fitted to a shaft extending in the main scanning direction, but may be rotatably supported by the main carriage 20. In this embodiment, a carriage movement type flat bed scanner will be described. However, the present invention can also be applied to a sheet feed scanner.

  The first lens 12 and the second lens 13 have different resolutions. The resolution for reading an image can be changed to the set resolution by localizing the optical axis of either the first lens 12 or the second lens 13 in the central optical path in accordance with the set resolution. The central optical path is an optical path that extends from the center of the main scanning line in a direction perpendicular to the main scanning line and reaches a predetermined pixel near the center of the image sensor 28 via the mirror 22. However, how to read the original 34 in a state where the optical axes of the first lens 12 and the second lens 13 are aligned with the image sensor 28 is a design matter that can be selected as appropriate. The state where the optical axis of the first lens 12 is localized in the central optical path is the first state described in the claims, and the state where the optical axis of the second lens 13 is localized in the central optical path is described in the claims. Corresponds to the second state. To switch between the first state and the second state, the CPU 60 controls the lens unit controller 66 in accordance with the type and resolution setting of the document input by the user on the PC (not shown) connected via the external interface controller. This is performed by moving the lens unit 10 so that the optical axis of the first lens 12 or the second lens 13 is positioned on the central optical path in accordance with the type and the set resolution. The first lens 12 and the second lens 13 may be lenses having the same resolution.

FIG. 1 is a plan view of the lens unit 10 as viewed from the document table 32 side.
The first lens barrel 100 is fixed to the lens carriage 14 by the first holder 102. The first holder 102 corresponds to the lens adjustment unit described in the claims. The first holder 102 is formed in a cylindrical shape whose inner diameter substantially matches the outer diameter of the first lens barrel 100. The first lens barrel 100 is positioned with respect to the first holder 102 by a fixing screw 104 inserted into an annular groove 101 formed in the first lens barrel 100. The first holder 102 is fixed to the lens carriage 14 by an adjustment screw 108 that is screwed into a female screw 110 formed on the lens carriage 14. The second lens barrel 115 is accommodated in a semi-cylindrical groove 114 formed in the lens carriage 14, and is sandwiched between the second holder 116 and the lens carriage 14 fixed to the lens carriage 14 by a fixing screw 118.

  Here, a structure for adjusting the mounting posture and the mounting position of the first lens barrel 100 will be described in detail. The first holder 102 has a plate-like protrusion 113 that is parallel to the document table 32. The protrusion 113 is placed on a wall surface 14 f that is parallel to the document table 32 of the lens carriage 14. The protrusion 113 is formed with an adjustment hole 106 into which the adjustment screw 108 is inserted. The adjustment screw 108 corresponds to the lens adjustment unit described in the claims. The diameter d1 of the circular adjustment hole 106 is larger than the outer diameter d2 of the shaft portion of the adjustment screw 108. Therefore, in a state where the first holder 102 is not pressed and fixed to the lens carriage 14 with the adjustment screw 108 with the washer 112 interposed therebetween, the first holder 102 is within a range in which the adjustment screw 108 can move within the adjustment hole 106. The first lens barrel 100 can be freely moved on a plane parallel to the document table 32.

The configuration of the image scanner 1 according to the first embodiment of the present invention has been described above. next,
An example of a method for adjusting the mounting position and mounting posture of the first lens 12, the second lens 13, and the image sensor 28 in the image scanner 1 will be described.
FIGS. 5A, 5 </ b> B, and 5 </ b> C are schematic diagrams illustrating a method for adjusting the mounting position and mounting posture of the first lens 12, the second lens 13, and the image sensor 28. First, as shown in FIG. 5A, the second lens 13 fixed to the lens carriage 14 is brought into a second state where the optical axis is localized in the central optical path. Next, a test chart 120 on which a stripe pattern 122 for detecting MTF (amplitude transfer function), a mark 124 for detecting a central optical path, and the like are drawn is placed on the document table 32. Next, the test chart is read by the image scanner 1 and the light receiving surface of the image sensor 28 is perpendicular to the optical axis of the second lens 13 using a monitor 126 or the like that analyzes the output signal from the image sensor 28. In addition, the attitude and position of the image sensor 28 are adjusted so that the center of the image sensor 28 is positioned on the optical axis of the second lens. At this time, for example, the output level of the image sensor 28 corresponding to the brightness of the stripe pattern 122 is displayed in a waveform on the monitor 126 based on the output signal from the image sensor 28, and the pixel position corresponding to the mark 124 is the reference position. They are displayed overlapping. When the adjustment of the mounting position and mounting posture of the image sensor 28 is completed, the direction of the first lens 12 is adjusted. The posture adjustment and the position adjustment of the first lens 12 are performed as follows, for example, in a state where the motor 50 is rotated and the state is changed to the first state shown in FIGS. First, the image of the test chart 120 is read again by the image scanner 1. Next, while confirming the monitor 126, the first lens barrel 100 and the first holder 102 are moved with the adjustment screw 108 loosened so that the MTF is optimal. Further, while checking the monitor, the first lens barrel 100 and the first holder 102 are moved in a direction parallel to the light receiving surface of the image sensor 28 so that the pixel position corresponding to the mark 124 overlaps the reference position. In an optimally adjusted state, the entire light receiving surface of the image sensor 28 is within the depth of focus of the first lens 12, and the optical axis of the first lens 12 is perpendicular to the image sensor 28 and parallel to the optical axis of the second lens 12. Thus, the optical axis of the first lens 12 is localized in the central optical path. After the adjustment of the mounting posture and the mounting position of the first lens barrel 100 is completed, the adjustment screw 108 is tightened to fix the first lens barrel 100 to the lens carriage 14.

According to the first embodiment of the present invention, since the mounting posture and mounting position of the first lens 12 can be adjusted, the first lens 12 can be fixed to the lens carriage 14 at the optimal position and in the optimal posture. Therefore, it is possible to improve the reading accuracy in the image scanner 1 that reads the document by switching the first lens 12 and the second lens 13.
(Second embodiment)

  FIG. 6 is a schematic diagram of the lens unit 10 according to the second embodiment of the present invention. A first lens barrel (not shown) is fixed to the inner wall surface of the cylindrical first holder 102. The first holder 102 is screwed into the lens barrel table 130 and serves as a rotation center of the first holder 102, and a first adjustment screw 136 that passes through the first adjustment hole 134 and is screwed into the lens barrel table 130. Thus, the lens barrel table 130 is fixed. The shape of the first adjustment hole 134 is formed in an arc shape that can be swung within a certain range when the first holder 102 is swung with the fixing screw 132 as a swinging shaft. The lens barrel table 130 is a plate-like member parallel to the document table 32 and includes two second adjustment holes 140 that are long in the main scanning direction. The lens barrel table 130 is fixed to the lens carriage 14 by a second adjustment screw 138 that passes through the second adjustment hole 140. The first lens 12 can reciprocate in a direction parallel to the light receiving surface of the image sensor 28 when the second adjustment screw 138 is loosened.

  Since the lens unit 10 according to the second embodiment is configured as described above, when adjusting the direction of the optical axis of the first lens 12, the second adjustment screw 138 is tightened to the light receiving surface of the image sensor 28. The position in the parallel direction is fixed, the first adjustment screw 136 is loosened, the first holder 102 is pivoted about the fixing screw 132 to adjust the direction of the optical axis, and then the first adjustment screw 136 is tightened. Next, the second adjustment screw 138 is loosened, the lens barrel table 130 is moved in a direction parallel to the light receiving surface of the image sensor 28, and the position of the first lens 12 is adjusted. That is, in the lens unit 10 according to the second embodiment of the present invention, the process of adjusting the direction of the optical axis of the first lens 12 and the process of adjusting the position in the direction parallel to the light receiving surface of the image sensor 28 are sequentially performed separately. It can be carried out.

(Third embodiment)
FIG. 7 is a schematic diagram of the lens unit 10 according to the third embodiment of the present invention. The first lens barrel 100 (not shown) is fixed to the inner wall of the cylindrical first holder 102. The first holder 102 is locked to the first lens barrel table 164 so as to be swingable about the fixing screw 132. The third adjustment screw 162 is screwed into a nut 166 fixed to the first lens barrel table 164, and the tip is in contact with the first holder 102. One end of the adjustment spring 160 abuts on the first lens barrel table 164 and the other end is locked to the first holder 102. Since the adjustment spring 160 presses the first holder 102 in the direction in which the first holder 102 is pressed against the third adjustment screw 162, the first holder 102 is positioned at a position where it abuts against the tip of the third adjustment screw 162. When the third adjustment screw 162 is rotated, the first holder 102 rotates about the fixing screw 132 as a rotation axis according to the position of the tip of the third adjustment screw 162. That is, the direction of the optical axis of the first lens can be adjusted by rotating the third adjustment screw 162.

  The first lens barrel table 164 is a plate-like member parallel to the document table 32 and includes two third adjustment holes 170 that are long in the main scanning direction. The first lens barrel table 164 is fixed to the second lens barrel table 150 by a fourth adjustment screw 168 that passes through the third adjustment hole 170. When the third adjustment hole 170 is loosened, the first lens can reciprocate in the direction parallel to the light receiving surface of the image sensor 28 (main scanning direction) together with the first lens barrel table 164. The second lens barrel table 150 is a plate-like member parallel to the document table 32 and includes a fourth adjustment hole 154 that is long in the sub-scanning direction. The second lens barrel table 150 is fixed to the lens carriage 14 by a fifth adjustment screw 152 that passes through the fourth adjustment hole 154. In a state where the fifth adjustment screw 152 is loosened, the first lens 12 can reciprocate in the direction perpendicular to the light receiving surface of the image sensor 28 (sub-scanning direction) together with the second lens barrel table 150.

Since the lens unit 10 according to the third embodiment is configured as described above, the direction of the optical axis of the first lens fixed to the first holder 102 can be adjusted by rotating the third adjustment screw 162. it can. In a state where the fourth adjustment screw 168 is loosened, the first lens barrel table 164 is moved in a direction parallel to the light receiving surface of the image sensor 28, so that the position of the first lens in the direction parallel to the light receiving surface of the image sensor 28. Adjustments can be made. In a state where the fifth adjustment screw 152 is loosened, the second lens barrel table 150 is moved in a direction perpendicular to the light receiving surface of the image sensor 28, so that the position of the first lens in the direction perpendicular to the light receiving surface of the image sensor 28 is reached. Adjustments can be made. That is, the process of adjusting the direction of the optical axis of the first lens, the process of adjusting the position of the first lens in the direction parallel to the light receiving surface of the image sensor 28, and the direction perpendicular to the light receiving surface of the image sensor 28 of the first lens The process of adjusting the position can be sequentially performed in separate processes.
In the embodiment of the present invention, the second lens 13 is fixed and the position and orientation of the image sensor 28 are adjusted. However, the second lens 13 can be adjusted and the position and orientation of the image sensor 28 cannot be adjusted. It may be. Further, although an example in which the present invention is applied to an image scanner has been described, the present invention can also be applied to a facsimile, a copying machine, a multifunction machine, and the like.

1 is a plan view of a lens unit according to a first embodiment of the present invention. 1 is a schematic diagram showing an internal structure of an image scanner according to a first embodiment of the present invention. 1 is a block diagram showing an image scanner according to a first embodiment of the present invention. 1 is a perspective view of a lens unit according to a first embodiment of the present invention. The schematic diagram which concerns on the 1st Example of this invention. The schematic diagram of the lens unit which concerns on the 2nd Example of this invention. The schematic diagram of the lens unit which concerns on the 3rd Example of this invention.

Explanation of symbols

12: first lens, 13: second lens, lens switching unit 14: lens carriage, 28: image sensor, 32: document table (platen), 50: motor (lens switching unit), 52: drive transmission mechanism (lens switching) Part), 100: first lens barrel, 102: first holder (lens adjusting part), 108: adjusting screw (lens adjusting part), 115: second lens barrel

Claims (3)

A platen,
An image sensor;
A first barrel,
A first lens for forming an image on the image sensor, which is held by the first lens barrel and positioned on the platen;
A lens carriage capable of mounting the first lens barrel in a posture in which the optical axis of the first lens is oriented in an arbitrary direction;
A lens adjustment unit that fixes the first lens barrel to the lens carriage in a posture in which the optical axis of the first lens is directed in an arbitrary direction;
A second lens barrel mounted on the lens carriage;
A second lens for forming an image on the image sensor, which is held by the second lens barrel and positioned on the platen;
A lens that switches between a first state in which the first lens is positioned on an optical path from the document to the image sensor and a second state in which the second lens is positioned on the optical path by driving the lens carriage. A switching unit;
An image reading apparatus comprising: The lens carriage is mounted with the first lens barrel so as to be capable of reciprocating in a direction perpendicular to the light receiving surface of the image sensor,
The image reading apparatus according to claim 1, wherein the lens adjustment unit fixes the first lens barrel to the lens carriage at a position at an arbitrary distance from the light receiving surface. The lens carriage is mounted with the first lens barrel so as to be capable of reciprocating in a direction parallel to the light receiving surface of the image sensor,
The image reading apparatus according to claim 1, wherein the lens adjustment unit fixes the first lens barrel to the lens carriage at an arbitrary position on a plane parallel to the light receiving surface.

Images