Imaging optical mechanism, reading module, and image reading apparatus

An imaging optical mechanism includes a first concave mirror and a second concave mirror at a position shifted from the first concave mirror in a sub-scanning direction. A plurality of aperture members in which slits are formed is disposed between the first concave mirror and the second concave mirror. The first concave mirror reflects light incident from an original document so as not to be imaged at a position between the first concave mirror and the second concave mirror in the sub-scanning direction, and reflects light incident from the original document so as to be imaged at the position between the first concave mirror and the second concave mirror in a main scanning direction. The second concave mirror reflects light which is reflected by the first concave mirror and incident thereto, so as to be imaged at a position of a sensor.

CROSS REFERENCES TO RELATED APPLICATIONS

The entire disclosure of Japanese Patent Application Nos. 2018-003805, filed Jan. 12, 2018 and 2018-109026, filed Jun. 6, 2018 are expressly incorporated by reference herein.

BACKGROUND

1. Technical Field

The present disclosure relates to an imaging optical mechanism which is mounted in an optical module which moves relative to a reading target or an imaging object and images the reading target at the imaging object by causing light reflected by the reading target or light emitted from a light source to be incident to the imaging object, a reading module, and an image reading apparatus.

2. Related Art

In the related art, a scanner device including a carriage having a reading module that moves relative to an original document as a reading target and reads the original document is known as an example of an image reading apparatus. The scanner device is configured as an independent device or as a part of a multifunction device. The reading module includes a light source such as a linear light source, that irradiates an original document on a glass plate with light from below a document stand, an imaging optical mechanism that condenses light which has been reflected by the original document and then incident thereto, and a light receiving sensor (an example of an imaging object) on which an image of light emitted from the imaging optical mechanism is formed. A mechanism using a lens array as a component for a condensing function is known as the imaging optical mechanism. The configuration using the lens array has a problem of aberration occurring by refraction of light and has a tendency of the manufacturing cost increasing.

For example, JP-A-2006-62227 discloses an optical printer including a writing module that writes an image on a rotating photosensitive drum by performing imaging on the photosensitive drum as an imaging object with light of a light source image. The writing module includes plural sets of concave mirrors and an imaging optical mechanism that reflects the incident light by a plurality of concave mirrors so as to condense the light. The imaging optical mechanism is disposed in a state where a first concave mirror and a second concave mirror have been inclined while reflection surfaces thereof face each other. Imaging of an intermediate image of a light source image at an imaging position by the first concave mirror is performed at a predetermined position by the second concave mirror. The imaging optical mechanism is configured in a manner that plural sets of reflection elements (one set of reflection elements includes the first concave mirror and the second concave mirror) are arranged. The adjacent reflection elements are separated from a light blocking member having a thin plate shape. The light blocking member prevents an occurrence of a situation in which reflected light from any one set of reflection elements is incident to the adjacent reflection elements as stray light.

In the imaging optical mechanism disclosed in JP-A-2006-62227, effects of blocking stray light from the adjacent reflection element by providing the light blocking member, improving contrast of an image to be formed, and increasing a resolution of an image to be written on the imaging object are obtained. In a case where the imaging optical mechanism disclosed in JP-A-2006-62227 is applied to a reading module of an image reading apparatus, effects of blocking stray light from the adjacent reflection element by providing the light blocking member, improving contrast of an image formed on the light receiving sensor as an imaging object, and increasing a reading resolution of the sensor are obtained.

However, in an image reading apparatus requiring a higher reading resolution or an apparatus such as an optical printer, which requires a higher writing resolution, the contrast of an image of light to be formed on the imaging object is insufficient. As a result, the sufficient resolution is not obtained. It is necessary that an arrangement pitch of the reflection element is reduced by increasing the required resolution. However, providing the light blocking member at a very small pitch may have a difficulty in manufacturing.

SUMMARY

An advantage of some aspects of the disclosure is to provide an imaging optical mechanism, a reading module, and an image reading apparatus in which an image of light can be formed on an imaging object at high contrast and a high resolution can be obtained.

Hereinafter, means of the disclosure and operation effects thereof will be described.

According to an aspect of the disclosure, an imaging optical mechanism is mounted in an optical module that moves relative to a reading target or an imaging object and images, on the imaging object, light incident by reflecting or transmitting light from a light source by or through the reading target or light incident from the light source. The imaging optical mechanism includes a first specular surface that reflects the light incident from the reading target, a second specular surface that is disposed at a position shifted from the first specular surface in a relative movement direction of the optical module and reflects and emits light reflected by the first specular surface, and a plurality of aperture members in which slits are formed along a path in which the light incident from the reading target travels toward the first specular surface, a path in which the light reflected by the first specular surface travels toward the second specular surface, and a path in which the light reflected by the second specular surface travels toward the imaging object. The first specular surface has a first curvature at which the light which is widely incident from the reading target in the movement direction is reflected so as not to be imaged at a position between the first specular surface and the second specular surface, and a second curvature at which the light which is widely incident from the reading target in an intersection direction intersecting the movement direction is reflected so as to be imaged at a position between the first specular surface and the second specular surface. The second specular surface has a third curvature at which the light incident from the first specular surface in the movement direction is reflected so as to be imaged at a position of the imaging object, and a fourth curvature at which the light incident from the first specular surface in the intersection direction is reflected so as to be imaged at the position of the imaging object.

According to the configuration, light incident from the light source or light incident by reflecting the light from the light source by the reading target is imaged in the imaging object through a path in which light travels toward the first specular surface, a path in which the light reflected by the first specular surface travels toward the second specular surface, and a path in which the light reflected by the second specular surface travels toward the imaging object. At this time, only light passing through the slit of the aperture member in each of the paths of the light is imaged in the imaging object. Thus, stray light is blocked by the plurality of aperture members, and an occurrence of a situation in which the stray light reaches the imaging object is suppressed. As a result, contrast of an image formed in the imaging object is improved, and a high resolution can be obtained. Regarding light which is widely incident from the reading target, light incident to portions other than the first specular surface is blocked by the first light blocking member and is reflected by the first specular surface in the movement direction so as not to be imaged at a position between the first specular surface and the second specular surface, and is reflected by the first specular surface in the intersection direction so as to be imaged at the position between the first specular surface and the second specular surface. The light which has been reflected by the first specular surface and then incident in the movement direction is reflected by the second specular surface so as to be imaged at the position of the imaging object. The light which has been reflected by the first specular surface and then incident in the intersection direction intersecting the movement direction is reflected by the second specular surface so as to be imaged at the position of the imaging object. Thus, light from the reading target is imaged as an inverted image, in the imaging object in the movement direction and is imaged as an erected image, in the imaging object in the intersection direction. In the movement direction, considering an overlap of an image is not required because the adjacent concave mirror is not provided. Therefore, imaging may occur slightly, and thus it is possible to secure lengths of the first specular surface and the second specular surface in the movement direction to be relatively long. Therefore, it is possible to secure the large quantity of light imaged in the imaging object, and thus to secure brightness of an image. As a result, it is possible to form an image having high contrast in the imaging object and to obtain high resolution. Since light is reflected by the first specular surface and the second specular surface, an optical path length from the reading target to the imaging object increases, and thus it is possible to increase a focal distance. Therefore, it is possible to increase a focal depth. Accordingly, it is possible to form an image of light in the imaging object at high contrast and to obtain a high resolution.

In the imaging optical mechanism, preferably, lengths of the first specular surface and the second specular surface in the movement direction are longer than lengths of the first specular surface and the second specular surface in the intersection direction.

According to this configuration, the large quantity of light can be incident and reflected to and by the first specular surface and the second specular surface. Thus, it is possible to secure brightness of an image formed in the imaging object. If the lengths of the first specular surface and the second specular surface are too long, the focal depth in the movement direction is shallow. Thus, the lengths thereof are preferably set to be long in a range causing the focal depth not to be shallow.

Preferably, the imaging optical mechanism further includes a first light blocking member which is disposed on a path and has a slit at a position facing the first specular surface, the path in which the incident light travels toward a first aperture member disposed on a most incident side of the light among the plurality of aperture members, and a second light blocking member which is disposed on a path and has a slit at a position facing the second specular surface, the path in which the light reflected by the second specular surface is transmitted through a second aperture member disposed on a closest side to the imaging object among the plurality of aperture members and travels toward the imaging object.

According to the configuration, light incident by passing through the slit of the first light blocking member among rays of light which is incident and spreads is reflected by the first specular surface through the slits of the plurality of aperture members. Since incident light is restricted at the slit in the movement direction by the first light blocking member, it is possible to secure the large quantity of light reflected by the first specular surface in the movement direction and to reduce stray light traveling toward portions other than the first specular surface, in particular, stray light which is directly incident to an imaging surface from the reading target such as an original document. The light reflected by the second specular surface passes through the slits of the plurality of aperture members, further passing through the slit of the second light blocking member, and then is imaged in the imaging object. Since the light reflected by the second specular surface is restricted by the slit of the second light blocking member in the movement direction, it is possible to reduce stray light in the movement direction in cooperation with the first light blocking member. Thus, brightness of an image formed in the imaging object is secured, high contrast can be obtained, and thus a high resolution can be obtained.

In the imaging optical mechanism, preferably, an end portion of an inside of at least one slit in the movement direction among slits formed in each of the first light blocking member and the second light blocking member is disposed at a position at which the light traveling toward portions other than the specular surfaces disposed to face each other is blocked.

According to the configuration, it is possible to suppress blurring of an image formed in the sensor and to secure brightness of the image by reducing stray light. Thus, it is possible to obtain imaging at high contrast.

In the imaging optical mechanism, preferably, a side surface of at least one slit, which is provided in the movement direction among the slits formed in each of the first light blocking member and the second light blocking member has an inclined shape widened toward an opposite side of the specular surfaces disposed to face each other.

According to the configuration, it is possible to block stray light incident from the slit of the first light blocking member without blocking reading light from an original document by the side surface disposed in the movement direction. Thus, it is possible to obtain imaging at high contrast.

In the imaging optical mechanism, preferably, a first light blocking portion is provided at a position of blocking light which is transmitted through the slit of the first light blocking member and travels toward the slit of the second light blocking member, in at least one of the first light blocking member and the second light blocking member.

According to the configuration, it is possible to reduce direct stray light in a manner that the first light blocking portion blocks the direct stray light which directly travels through the slit of the second light blocking member from the slit of the first light blocking member without passing through a path in which the light is reflected by the concave mirror. Thus, it is possible to obtain imaging at high contrast.

In the imaging optical mechanism, preferably, a second light blocking portion is provided at a position of blocking light which is transmitted through the slit of the first light blocking member and travels toward the slit of the second light blocking member, in at least one of the first aperture member and the second aperture member.

According to the configuration, it is possible to reduce direct stray light which directly travels through the slit of the second light blocking member from the slit of the first light blocking member without passing through a path in which the light is reflected by the concave mirror, by the second light blocking portion. Thus, it is possible to obtain imaging at high contrast.

In the imaging optical mechanism, preferably, in a case where the second light blocking portion is provided in the first aperture member, the second light blocking portion is provided at a position between a path of light restricted by the slit of the first light blocking member and a path of light to be incident to the second specular surface and light reflected by the second specular surface, in the slit formed in the first aperture member. In addition, preferably, in a case where the second light blocking portion is provided in the second aperture member, the second light blocking portion is provided at a position between a path of light to be incident to the first specular surface and light reflected by the first specular surface and a path of light reflected by the second specular surface, in the slit formed in the second aperture member.

According to the configuration, it is possible to effectively reduce direct stray light by the second light blocking portion without totally blocking light passing through a path in which the light is reflected by the first concave mirror and the second concave mirror.

In the imaging optical mechanism, preferably, a side surface of the second light blocking portion in the movement direction has a shape along an inner end portion of the path of the light restricted by the slit of the first light blocking member and the paths of the light to be incident to the second specular surface and light reflected by the second specular surface.

According to the configuration, it is possible to block direct stray light by the second light blocking portion.

In the imaging optical mechanism, preferably, an inclined surface inclined toward an opposite side of the second specular surface from the movement direction is provided in a region adjacent to a region of the slit, to which the light is incident, on a surface of at least the first aperture member of the first aperture member and the second aperture member, on the reading target side.

According to the configuration, it is possible to reduce stray light occurring by reflecting light incident to a region adjacent to the slit of the first aperture member, from the slit of the first light blocking member.

In the imaging optical mechanism, preferably, a width of the slit of the first light blocking member in the movement direction corresponds to a length as long as light incident from the reading target can be restricted to an irradiation area of the first specular surface in a length range in the movement direction.

According to the configuration, the light incident from the reading target is restricted by the slit of the first light blocking member in the movement direction, and thus it is possible to block light out of the length range of the first specular surface in the movement direction. Accordingly, high contrast can be obtained by brightening an image of light formed in the imaging object. As a result, a high resolution can be obtained.

In the imaging optical mechanism, preferably, a width of the slit of the second light blocking member in the movement direction corresponds to a length as long as light reflected by the second specular surface can be transmitted.

According to the configuration, all or most of rays of light other than the light reflected by the second specular surface are blocked by the second light blocking member. Accordingly, it is possible to secure brightness and high contrast of an image of light formed in the imaging object, and to obtain a high resolution.

In the imaging optical mechanism, preferably, the first specular surface and the second specular surface are disposed at positions which do not overlap each other in the movement direction and positions overlapping each other in the intersection direction.

According to the configuration, all or most of rays of light reflected by the first specular surface can be incident to the second specular surface, and it is possible to suppress an occurrence of a situation in which light other than the light reflected by the first specular surface is incident to the second specular surface. It is possible to block stray light which is directly incident to the imaging surface from a region out of a reading range of the reading target such as an original document, by the first light blocking member and the second light blocking member cooperating with each other. Accordingly, it is possible to secure brightness and high contrast of an image formed in the imaging object, and to obtain a high resolution.

In the imaging optical mechanism, preferably, an image of the reading target in the movement direction is formed to be an inverted image, and an image of the reading target in the intersection direction is formed to be an erected image, at the position of the imaging object.

According to the configuration, in a case where plural sets of first specular surfaces, second specular surfaces, and imaging objects are arranged in the intersection direction, an erected image is formed in the imaging object in the intersection direction. Thus, images can be joined between the imaging objects. Since an inverted image is formed in the movement direction, it is possible to reduce the curvatures of the first specular surface and the second specular surface in the movement direction and to reduce aberration. If small aberration is allowed in the movement direction so as to obtain aberration balance between the movement direction and the intersection direction, it is possible to increase a dimension of the concave mirror in the movement direction and to secure brightness as much as the aberration is allowed.

In the imaging optical mechanism, preferably, the first light blocking member is integrally formed with the second specular surface in a state of being adjacent to the second specular surface in a first direction in the movement direction, and the second light blocking member is integrally formed with the first specular surface in a state of being adjacent to the first specular surface in a second direction in the movement direction.

According to the configuration, it is possible to manufacture the imaging optical mechanism with a relatively small number of components including a component obtained by integrally forming the first light blocking member and the second specular surface with each other and a component obtained by integrally forming the second light blocking member and the first specular surface with each other.

In the imaging optical mechanism, preferably, the second specular surface causes the reflected light to be imaged at an optical distance equal to an optical distance between the reading target and the first specular surface.

According to the configuration, the component obtained by integrally forming the first light blocking member and the second specular surface with each other and the component obtained by integrally forming the second light blocking member and the first specular surface with each other can be commonly used, and thus it is possible to further reduce the number of components constituting the imaging optical mechanism.

In the imaging optical mechanism, preferably, the first specular surface and the second specular surface have a common shape.

According to the configuration, the component obtained by integrally forming the first light blocking member and the second specular surface with each other and the component obtained by integrally forming the second light blocking member and the first specular surface with each other can be used as common components, and thus it is possible to further reduce the number of components thereof.

In the imaging optical mechanism, preferably, the first light blocking member and the second light blocking member are integrally formed with the aperture member.

According to the configuration, it is possible to furthermore reduce the number of components constituting the imaging optical mechanism. In addition, arrangement position accuracy of the plurality of aperture members is improved, and the plurality of aperture members is easily arranged at positions as in an assumed design. Thus, it is possible to further reduce stray light. As a result, it is possible to form an image having high contrast in the imaging object.

According to another aspect of the disclosure, a reading module includes the imaging optical mechanism, a linear light source as the light source that irradiates the reading target with light in the intersection direction, and a sensor array in which a plurality of sensors as the imaging object is arranged. The reading module is provided as an example of the optical module. The imaging optical mechanism includes a first specular surface array in which a plurality of first specular surfaces is arranged in the intersection direction, a second specular surface array in which a plurality of second specular surfaces is arranged in the intersection direction, the first light blocking member which has the slit opening to allow light to be incident to the first specular surface array, and the second light blocking member which has the slit opening to allow light reflected by the second specular surface array to be imaged in the sensor array.

According to the configuration, it is possible to form a bright image of the reading target in the sensor array at high contrast by the reading module moving relative to the reading target. Accordingly, it is possible to read the reading target at a high resolution by the reading module.

In the reading module, preferably, the slit of the first light blocking member opens in a length range allowing light to be incident to the first specular surface array, in the intersection direction, and the slit of the second light blocking member opens in a length range allowing the light reflected by the second specular surface array in the intersection direction to be imaged in the sensor array.

According to the configuration, the slits of the first light blocking member and the second light blocking member open in the length range of the specular surface array in the intersection direction. Thus, it is possible to secure a large quantity of light incident to the imaging optical mechanism and a large quantity of light emitted from the imaging optical mechanism, and to secure brightness of an image formed in the sensor, for example, in comparison to a configuration in which a plurality of slits which opens to respectively correspond to specular surfaces is formed.

According to still another aspect of the disclosure, an image reading apparatus includes the reading module, a transparent member that defines a position of an original document as a reading target, and a transporting unit that relatively moves the original document and the optical module. The reading module reads the original document at a position on an opposite side of the original document with the transparent member interposed between the reading module and the original document, by causing reflected light of light with which the original document has been irradiated to be incident to the reading module. According to the configuration, the image reading apparatus can cause the reading module to read an original document as the reading target at a high resolution.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, embodiments obtained by embodying an image reading apparatus will be described with reference to the drawings. An image reading apparatus in a first embodiment is a multifunction device including a scanner device, for example.

As illustrated inFIG. 1, a multifunction device11includes a printing device21and a scanner device31. The printing device21performs printing on a medium P such as paper. The scanner device31is disposed on an upper side of the printing device21in a vertical direction Z and is capable of reading an original document D. The multifunction device11has functions of scanning, copying, and printing.

An operation panel13provided in a device body12of the multifunction device11includes a display unit14for displaying a menu screen and the like and an operation unit15configured with an operation switch and the like. For example, a request of scanning, copying, or printing is applied to the multifunction device11by operating the operation unit15. The request of printing is also applied to the multifunction device11from a host device which is connected to the multifunction device11through a communication cable and is configured with a personal computer (PC) or the like. The multifunction device11receives, for example, a scanning job at time of request of scanning or copying.

The printing device21performs printing on a medium P supplied (fed) from a cassette17inserted at the bottom of the device body12. The medium P after printing is discharged onto a stacker18from a discharge port21A of the device body12. The scanner device31reads an original document D and transfers image data obtained by the reading to the host device, for example. Copying is performed in a manner that the printing device21prints an image based on image data obtained by the scanner device31reading an original document D, on a medium P. Therefore, when scanning or copying is performed, an original document D is read by the scanner device31.

As illustrated inFIG. 1, the scanner device31includes a main body32and a document stand cover34. The main body32includes a flat-bed type document stand33(seeFIG. 2) on which an original document can be placed. The document stand cover34is capable of opening and closing the document stand33. In the example, a document transporting unit35is provided at a rear portion of the document stand cover34, which illustrated as an upper side inFIG. 1. The document transporting unit automatically transports a plurality of set original documents one by one. The document transporting unit35includes a set tray36and a transport mechanism unit37. A plurality of original documents D can be set on the set tray36. The transport mechanism unit37transports the original document D on the set tray36one by one. The transport mechanism unit37performs transporting which includes feeding of feeding an original document on the set tray36to a reading position and discharging of discharging an original document D after an image has been read. The original document D after image reading is discharged to, for example, a discharge region between the set tray36and the document stand cover34.

As illustrated inFIGS. 2 and 3, the main body32of the scanner device31includes a box-like case38having an opening portion at a portion facing the document stand cover34illustrated inFIG. 1. The document stand33is formed in a manner that a large glass plate40A having a quadrangle plate shape is fit into a large opening portion of the case38. A reading window39is formed in a manner that a small glass plate40B having a long quadrangle plate shape is fit into a small opening portion of the case38. The glass plate40A of the document stand33corresponding to a region on which an original document D to be read in a flat-bed manner is placed. The glass plate40A has a size which is slightly wider than the maximum document size allowed to be read by the scanner device31. The glass plate40B of the reading window39is provided at a reading position at which an image of an original document D transported from the document transporting unit35is read. In the embodiment, in a case where the glass plates40A and40B for defining the position of an original document D are not particularly distinguished from each other, the glass plates40A and40B are referred to as “a glass plate40”. The glass plate40is an example of a transparent member that defines the position of an original document D.

The document stand cover34illustrated inFIG. 1is pivotable between a closed state of pressing an original document D placed on the document stand33and an opened state when the original document D is set on the document stand33or the original document D after reading is removed, as illustrated inFIGS. 2 and 3. The scanner device31reads an original document D placed on the flat-bed type document stand33. An original document D fed into the transport mechanism unit37by the document transporting unit35illustrated inFIG. 1is sent out to a position which substantially faces the reading window39(seeFIG. 3) on the back surface of the document stand cover34in the closed state. An image is read on the reading window39, and then the original document D is discharged to the discharge region.

As described above, the scanner device31in the embodiment operates in two modes, that is, a flatbed (FB) mode of reading an original document D placed on the flat-bed type document stand33and an auto document feeder (ADF) of reading an original document D transported from the set tray36by the document transporting unit35, at the reading position corresponding to the reading window39in the middle of being transported.

As illustrated inFIG. 2, a reading module50as an optical module and a transporting unit60are provided in the case38. The optical module extends long in a main scanning direction X. The transporting unit60relatively moves the original document D (seeFIG. 3) and the reading module50in a sub-scanning direction Y. The transporting unit60includes a carriage61and a driving mechanism63. The carriage61has the reading module50mounted therein and is used for sensing. The driving mechanism63applies power for transporting (conveying) the carriage61along a guide rail62in the sub-scanning direction Y, to the carriage61.

As illustrated inFIG. 2, the reading module50includes a linear light source52and a reading element53. The linear light source52irradiates an original document D (seeFIG. 3) with light through glass plates40A and40B. The reading element53is disposed in the main scanning direction X which is a direction of the linear light source52extending and reads an original document D by causing light from the original document D to be incident thereto. The reading module50moves along with the carriage61in the sub-scanning direction Y and then reads an original document D. The reading module50has a length which is equal to or more than the maximum assumed width of an original document D in a longitudinal direction (main scanning direction X). As an example, the length of the reading module50is set to have a value which is slightly larger than, for example, the A3 size (width of 320 mm) or the A4 size (width of 210 mm) as the maximum assumed width of an original document D.

As illustrated inFIG. 2, the driving mechanism63includes an electric motor64as a power source of the carriage61and a power transmission mechanism65that transmits power of the electric motor64to the carriage61. The power transmission mechanism65includes an endless belt69which is wound around a driving pulley66and two driven pulleys67and68and pulls the carriage61. The driving pulley66rotates by the power of the electric motor64. The driven pulleys67and68are disposed at both end portions of a sheet metal member32A extending along the guide rail62. The carriage61is joined to a portion of a portion of the belt69, which has been stretched parallel to the guide rail62, with a joint61A. If the electric motor64drives to rotate forward, the carriage61moves (forward) in a forward direction Y1. If the electric motor64drives to rotate backward, the carriage61moves (backward) in a backward direction Y2. The reading module50reads an original document D placed on the document stand33in the middle of the carriage61moving along the guide rail62in the sub-scanning direction Y. The reading module50on the carriage61is electrically connected to a control unit100accommodated in the device body12, through a flexible cable54. The reading module50performs a reading operation in accordance with a command signal from the control unit100and outputs a reading signal obtained by reading an image of an original document D to the control unit100. The control unit100transfers reading data based on the reading signal to the host device (not illustrated).

In the document transporting unit35illustrated inFIG. 3, an original document is fed along a feeding path SP by a feeding roller (not illustrated) and plural pairs of feeding rollers73which constitute a portion of a feeding mechanism. The original document is pressed to the reading window39side, at the reading position in the middle of being transported, by the guide portion34A. The original document is read by the reading module50on the carriage61through the glass plate40B of the reading window39. The original document which has been read is discharged to the outside of the device from the transport mechanism unit37along a discharge path EP by plural pairs of discharge rollers74. As described above, in the ADF mode, a plurality of original documents D set in the set tray36(seeFIG. 1) is fed into the transport mechanism unit37one by one, and is read at the reading position in the middle of a transport path FP by the reading module50on the carriage61.

As illustrated inFIG. 3, a reading unit51is disposed in the transport mechanism unit37. The reading unit51is capable of causing a reading module50to read a surface (back surface) of an original document, which is on an opposite side of a reading surface (front surface) of the original document, in the middle of the discharge path EP. Therefore, the scanner device31is capable of reading both surfaces of an original document in the ADF mode. A reading timing of an original document at the reading position by the reading module50is determined based on a detection signal of a first detection unit76capable of detecting the original document in the middle of being fed. A reading timing of the original document by the reading unit51is determined based on a detection signal of a second detection unit77capable of detecting the original document in the middle of being discharged. The reading module50similar to the reading module50on the carriage61is mounted in the reading unit51.

As illustrated inFIG. 3, the reading module50mounted in the carriage61is disposed on an opposite side of a placing surface of an original document D in the glass plates40A and40B, and is positioned to face the back surfaces of the glass plates40A and40B. The reading module50includes the linear light source52, the reading element53, and a housing55. The housing55accommodates the linear light source52and the reading element53in a state where light transmission and light receiving are possible. Two white reference plates78and79are disposed at the upper surface portion of the main body32(also seeFIG. 1) of the scanner device31. The white reference plates78and79are used as a reading target when white reference data for shading correction is obtained and have uniform reflection surfaces with high reflectance.

When a reading operation is performed in the FB mode, the carriage61indicated by a two-dot chain line inFIG. 3moves in the forward direction Y1, and thereby an original document D on the glass plate40A is read by the reading module50. The carriage61after the original document D has been read moves from the position at which the reading has ended, in the backward direction Y2and comes back to a standby position.

As described above, in the multifunction device11, an original document D moves to the reading module50in the sub-scanning direction Y in the ADF mode, and the reading module50moves to the original document D on the glass plate40A in the sub-scanning direction Y in the FB mode. Even in any mode of the ADF mode and the FB mode, the reading module50relatively moves to the original document D in the sub-scanning direction Y and reads an image of the original document D with a sensor573illustrated inFIG. 5. In the embodiment, the sub-scanning direction Y corresponds to a movement direction in which the reading module50relatively moves to the original document D as an example of a reading target. The main scanning direction X corresponds to an intersection direction intersecting the movement direction.

Next, a detailed configuration of the reading module50will be described with reference toFIG. 4. As illustrated inFIG. 4, the reading module50that relatively moves to an original document D on the glass plate40includes the linear light source52and the reading element53. The linear light source52irradiates the original document D with light through the glass plate40. The reading element53condenses and receives light reflected from a reading surface Dp of the original document D. Light transmission of the linear light source52to the reading surface Dp and light receiving of reflected light from the reading surface Dp by the reading element53are possible through an opening55A at a portion facing the glass plate40.

The linear light source52illustrated inFIG. 4is disposed at a posture in which a principal axis L1of light in the linear light source52is inclined from a direction of a normal line N1of the glass plate40or the reading surface Dp at an angle θ1. The linear light source52includes a luminous body521such as an LED and a light guide522, for example, as a light guiding member that guides light emitted from the luminous body521, in the main scanning direction X and guides the light in a direction of forming an angle θ1. The light guide522has a rod shape formed with transparent resin such as acrylic resin. The light guide522guides light from the luminous body521so as to illuminate a band-like area of the reading target at uniform brightness. As illustrated inFIG. 4, the principal axis L1of light output from the light guide522forms a predetermined angle with the glass plate40. Therefore, regular reflected light of an original document D is not incident to the reading element53, and scattered reflected light from the original document D is incident to the reading element53. A direction of a principal axis of light L2which is reflected by the original document D and then incident to the reading element53is referred to as an optical axis direction Z1of the reading element53. In the example, the optical axis direction Z1of the reading element53is identical to the vertical direction Z which is a direction perpendicular to the glass plate40.

FIG. 5illustrates the reading element53in an example in which a contact image sensor module (also referred to as “a CISM” below)530is used as the reading module50. The CISM530is a linear image sensor. As illustrated inFIG. 5, the reading element53constituting the CISM530is disposed in the main scanning direction X which is a direction of the linear light source52(seeFIG. 4) extending. The reading element53includes an imaging optical mechanism56and a light receiving element57. The imaging optical mechanism56causes scattered light which has been reflected from an original document D to be incident thereto and condenses the scattered light. The light receiving element57receives an image of light condensed by the imaging optical mechanism56. The imaging optical mechanism56and the light receiving element57are mounted in the reading module50(CISM530), in a state of extending in the main scanning direction X. The imaging optical mechanism56and the light receiving element57are disposed in an order from the component close to the glass plate40. The imaging optical mechanism56faces the glass plate40at a relatively close position. The imaging optical mechanism56has a function of imaging scattered reflected light which has been incident from the reading surface Dp of an original document D, on a light receiving surface of the light receiving element57. The imaging optical mechanism56is provided for imaging light incident to a slit811, in the light receiving element57.

The imaging optical mechanism56illustrated inFIG. 5includes a casing80having a slit811which extends in the main scanning direction X. Constituent components of an imaging optical system are accommodated in the casing80. Scattered light which has been reflected by an original document D is incident from the slit811. Light L2incident from the slit811is reflected twice on an optical path indicated by an arrow of a one-dot chain line inFIG. 5, in the imaging optical system in the casing80. Then, the light L2is emitted from a second slit821illustrated inFIG. 7, and then is imaged in the light receiving element57. That is, an optical path length from an original document D to the light receiving element57is set to a focal distance, and an image of the reading surface Dp is formed in the light receiving element57. In the CISM530, incident light is reflected twice in the casing80, and thereby a long optical path length is secured. Thus, the focal depth becomes deep.

The light receiving element57illustrated inFIG. 5includes a substrate571and a sensor array572in which a plurality of sensors573is mounted on the substrate571to be arranged in line. The sensor array572includes a plurality (for example, 15500 pieces in a case of the A3 size (length of 310 mm)) of sensors573arranged in line in the main scanning direction X. With the sensor array572, an image of “one line” in the main scanning direction X can be captured. In the embodiment, the sensor573configures an example of an imaging object.

The imaging optical mechanism56illustrated inFIG. 6includes a first light blocking member81, a second light blocking member82, and a plurality of aperture members83and84. The first light blocking member81has a plate shape and includes a first slit811for causing light to be incident thereto. The second light blocking member82has a plate shape and includes a second slit821for causing light to be emitted. The plurality of aperture members83and84is disposed to be spaced from each other between the first light blocking member81and the second light blocking member82in the optical axis direction Z1. In the example, the two aperture members83and84are provided. The two aperture members83and84are set as a first aperture member83and a second aperture member84in an order from an upstream side in a light incident direction. The first aperture member83includes a plurality of slits831opening at a predetermined pitch in the main scanning direction X. The second aperture member84also includes a plurality of slits841opening at a predetermined pitch in the main scanning direction X. The imaging optical mechanism56includes a first concave mirror array851and a second concave mirror array861. The first concave mirror array851is an example of a first specular surface array in which first concave mirrors85as an example of first specular surfaces are arranged at a predetermined pitch in line in the main scanning direction X. The second concave mirror array861is an example of a second specular surface array in which second concave mirrors86as an example of second specular surfaces are arranged at a predetermined pitch in line in the main scanning direction X.

As illustrated inFIG. 6, the first light blocking member81and the second light blocking member82face each other in the vertical direction Z which is perpendicular to the reading surface Dp of an original document D. Two outer wall members87and88face each other in the sub-scanning direction Y. The members81,82,87, and88constitute a quadrangle tubular casing which extends long in the main scanning direction X.

FIG. 7illustrates the main configuration for an imaging function in the imaging optical mechanism56with omitting illustrations of the outer wall members87and88in the casing80.FIGS. 7, 9, and the like illustrate a configuration in which the overall length of the imaging optical mechanism56in the main scanning direction X is schematically shorter than the practical length thereof. As illustrated inFIGS. 6 and 7, the first light blocking member81facing the glass plate40on which an original document D is placed has a quadrangular plate shape. In the first light blocking member81, the first slit811which extends in the main scanning direction X, is penetrated in the optical axis direction Z1, and is used for causing light to be incident thereto opens. In the configuration in the example, the first slit811has a length corresponding to the width of an original document D as the reading target in the main scanning direction X, and has a width having a predetermined value in a range of, for example, 0.5 mm to 1 mm in the sub-scanning direction Y. The second light blocking member82has a quadrangular plate shape similar to the first light blocking member81and is disposed at a position which faces the first light blocking member81to be spaced at a predetermined distance from the glass plate40. In the second light blocking member82, the second slit821extending in the main scanning direction X opens at a position shifted from the first slit811in the sub-scanning direction Y. The second slit821has an opening shape and an opening size which are similar to those of the first slit811. That is, the second slit821has a length corresponding to the width of an original document D as the reading target in the main scanning direction X, and has a width having a predetermined value in a range of, for example, 0.5 mm to 1 mm in the sub-scanning direction Y.

As illustrated inFIGS. 7 to 9, the second light blocking member82includes the first concave mirror array851at a position facing the first slit811of the first light blocking member81. In the first concave mirror array851, the plurality of first concave mirrors85is arranged at a predetermined pitch in a line in the main scanning direction X. The first concave mirror85reflects light incident from an original document D.

As illustrated inFIGS. 7 to 9, the first light blocking member81includes the second concave mirror array861at a position facing the second slit821of the second light blocking member82. In the second concave mirror array861, the plurality of second concave mirrors86is arranged at a predetermined pitch in a line in the main scanning direction X. The second concave mirror86is disposed at a position shifted from the first concave mirror85in the sub-scanning direction Y which is a relative movement direction of the reading module50. The second concave mirror86reflects and emits light reflected by the first concave mirror85.

As illustrated inFIGS. 7 to 9, the first aperture member83and the second aperture member84having a lattice shape are disposed between the first light blocking member81and the second light blocking member82, so as to be parallel to each other in a state of being spaced at a predetermined gap. A gap G1(FIG. 9) between the first light blocking member81and the first aperture member83, a gap G2(FIG. 9) between the second aperture member84and the second light blocking member82, and a gap G3(FIG. 9) between the first aperture member83and the second aperture member84are set to a distance as long as stray light is suppressed. The stray light in incident light disturbs forming of an image at a reading target position P1in the sensor573. That is, the relative positions of the plurality of aperture members83and84in the optical axis direction Z1are set to be positions allowing the stray light to be effectively suppressed, between the first light blocking member81and the second light blocking member82. The first light blocking member81, the first aperture member83, the second aperture member84, and the second light blocking member82are disposed to be parallel to each other at the gaps G1to G3in the optical axis direction Z1.

The first aperture member83includes the plurality of slits831which has a predetermined width, is disposed at a predetermined pitch in the main scanning direction X, and is long holes extending with a predetermined length in the sub-scanning direction Y. The second aperture member84has the same shape and the same size as those of the first aperture member83. The second aperture member84includes the plurality of slits841which has a predetermined width, is disposed at a predetermined pitch in the main scanning direction X, and is long holes extending with a predetermined length in the sub-scanning direction Y. The slits831and841are positioned to correspond to the concave mirrors85and86in the optical axis direction Z1, respectively.

As illustrated inFIGS. 7 and 8, the first light blocking member81has a slit811at a position facing the first concave mirror85. The slit811is disposed on a path in which light incident from the reading target position P1travels toward the first aperture member83which is disposed on an incident side (original document D side) of light among the plurality of aperture members83and84. The second light blocking member82has a slit821at a position facing the second concave mirror86. The slit821is disposed on a path in which light reflected by the second concave mirror86passes through the second aperture member84disposed on a side close to the sensor573among the plurality of aperture members83and84and travels toward the sensor573.

Widths S1and S2of the slits811and821of the first light blocking member81and the second light blocking member82in the sub-scanning direction Y are set to values in a range of 0.5 mm to 1.0 mm as an example. The widths are 0.7 mm, for example. If the widths S1and S2of the slits811and821in the sub-scanning direction Y are large, stray light does not abut on the first concave mirror85, and but passes through the slit821, and then is incident to the sensor573. Alternatively, light reflected by an inner wall surface of the second light blocking member82other than the first concave mirror85is incident to the second concave mirror86, and acts as the cause of stray light. If the width S1of the slit811is too small, the quantity of light incident to the first concave mirror85becomes small, and an image of light formed in the sensor573becomes dark. Therefore, the width S1of the slit811is set to have a value allowing the entirety of the region of the first concave mirror85in the sub-scanning direction Y to be irradiated with light from the slit811. The slit811of the first light blocking member81opens in a length range allowing light to be incident to the first concave mirror array851in the main scanning direction X. The stray light is not a problem if the sensor573does not receive the stray light.

As illustrated inFIG. 8, in the plurality of aperture members83and84, the slits831and841open in a range covering a path in which light LA incident from an original document D in the sub-scanning direction Y travels toward the first concave mirror85, a path in which light LB reflected by the first concave mirror85travels toward the second concave mirror86, and a path in which light LC reflected by the second concave mirror86travels toward the sensor573.

The slits831and841of the two aperture members83and84are positioned to face the first concave mirror85and the second concave mirror86in the optical axis direction Z1. Therefore, the width center of each of the slits831and841in the main scanning direction X coincides with the width center of each of the first concave mirror85and the second concave mirror86. The slits831and841are arranged at a pitch which is equal to the pitch of the first concave mirror85and the second concave mirror86. The widths of the slits831and841in the main scanning direction X are set to be dimensions causing light which passes through the slit831among rays of scattered light incident from the slit811and further passes through the slit841at the same position in the main scanning direction X to be applied to the range of the first concave mirror85in the main scanning direction X and not to be applied to portions other than the above range.

Here, if the widths of the slits831and841in the main scanning direction X are too wide, an effect of suppressing stray light is deteriorated. If the widths of the slits831and841in the main scanning direction X are too narrow, the stray light can be suppressed, but an image formed in the sensor573becomes dark. The relative positions and gaps of the two aperture members83and84to the first light blocking member81and the second light blocking member82in the optical axis direction Z1are set such that light can be blocked at portions of the aperture members83and84other than the slits831and841and stray light reaching the sensor573can be effectively suppressed.

For example, if one aperture member is provided, it is necessary that the aperture member becomes thicker in the optical axis direction Z1in order to suppress stray light. In this case, the width of the slit becomes 1 mm and the thickness thereof becomes about 10 mm. Thus, manufacturing in injection molding has a difficulty, and the quantity of stray light increases by reflection from a wall surface of the slit. Therefore, in the embodiment, the plurality of aperture members83and84are disposed between the two light blocking members81and82, at a gap in the optical axis direction Z1. Thus, the total thickness of the aperture members83and84in the optical axis direction Z1is relatively reduced, and stray light which has passed through the one aperture member is blocked more on the front surface of the one aperture member. One aperture member may be provided so long as stray light is suppressed so as to form an image having required contrast and to obtain a required resolution. A plurality of aperture members means that a plurality of aperture portions being plate-like portions which have a slit in which the width in the sub-scanning direction Y is wider than the width in the main scanning direction X is disposed at a position between the first concave mirror85and the second concave mirror86in the optical axis direction Z1, at a gap. For example, in the specification, even though the aperture member is configured with one component obtained by integrally forming two aperture members83and84, if two aperture portions are disposed at a gap in the optical axis direction Z1, the number of the plurality of aperture members83and84is considered as being two.

An anti-reflection treatment for suppressing regular reflected light by scattering light reflected by the surfaces is performed on inner wall surfaces of the first light blocking member81and the second light blocking member82and wall surfaces of the aperture members83and84. The anti-reflection treatment is a black matting treatment or a sand blasting treatment. For example, the light blocking members81and82and the aperture members83and84are formed with black synthetic resin or are obtained by performing a sand blasting treatment or black matting coating on surfaces of the members81to84after molding. In a case where the sand blasting treatment is performed, synthetic resin used for molding may have any color, but a color having low brightness is preferable. After molding with black synthetic resin has been performed, it is preferable that the sand blasting treatment be performed on the surface.

As illustrated inFIG. 8, the first concave mirror85and the second concave mirror86are disposed at positions shifted in the sub-scanning direction Y so as not to overlap each other. As illustrated inFIG. 9, the first concave mirror85and the second concave mirror86are disposed at positions overlapping each other in the main scanning direction X. As illustrated inFIG. 8, the first light blocking member81is integrally formed with the second concave mirror86in a state of being adjacent to the second concave mirror86in a first direction of the second concave mirror86in the sub-scanning direction Y. The second light blocking member82is integrally formed with the first concave mirror85in a state of being adjacent to the first concave mirror85in a second direction of the first concave mirror85in the sub-scanning direction Y. Here, the first direction and the second direction are directions which are opposite to each other in the sub-scanning direction Y. In the example illustrated inFIGS. 2 and 4, the first direction is set as a backward direction Y2, and the second direction is set as a forward direction Y1. Therefore, a position relationship in which the first concave mirror85faces the slit811of the first light blocking member81in the optical axis direction Z1, and the second concave mirror86faces the slit821of the second light blocking member82in the optical axis direction Z1is made.

The first concave mirror85and the second concave mirror86are provided at a pitch equal to a pitch of the sensor573in the main scanning direction X such that the number of concave mirrors85and86is equal to the number of sensors573. That is, the positions of the concave mirrors85and86constituting the concave mirror arrays851and861illustrated inFIGS. 7 and 9and the pitch between the concave mirrors85and86, in the main scanning direction X, are set to match with positions of the sensors573constituting the sensor array572illustrated inFIG. 5and the pitch between the sensors573, in the main scanning direction X. 15500 sensors573are disposed if the A3 size (length of 310 mm) at a width of 20 μm per one pixel is provided. An image formed in the adjacent concave mirror in the main scanning direction X overlaps a portion of an image formed in the adjacent concave mirror, and thus imaging is performed on the overall width of an original document without breaks. For example, if an image is read with RGB colors, three sensor arrays572are disposed independently for RGB. As illustrated inFIG. 8, both the concave mirrors85and86are inclined, at a predetermined inclination angle, so as to cause both the concave surfaces to face each other with respect to a virtual surface orthogonal to the optical axis direction Z1such that reflected light obtained by reflecting incident light by the first concave mirror85travels toward the second concave mirror86, and reflected light obtained by further reflecting the reflected light by the second concave mirror86travels toward the sensor573. The positions of the slits831and841and the pitch between the slits831and841in the main scanning direction X are identical to positions of the concave mirrors85and86and the pitch between the concave mirrors85and86in the main scanning direction X.

As illustrated inFIG. 9, in the imaging optical mechanism56in the embodiment, a unit imaging element SL is configured by a portion which constitutes one set of concave mirrors85and86(having the same position in the main scanning direction X) and one set of slits831and841(having the same position in the main scanning direction X) and corresponds to one width of an array pitch in the main scanning direction X. The imaging optical mechanism56is configured in a manner that a plurality of unit imaging elements SL is arranged in a line in the main scanning direction X. The first concave mirrors85and the second concave mirrors86are set to have a pitch dimension of a value, for example, in a range of 1.0 mm to 3.0 mm, in the main scanning direction X. As an example, the concave mirrors85and86are arranged at a pitch of 1.6 mm. The pitch of the slits831and841in the main scanning direction X is equal to the pitch of the concave mirrors85and86, that is, 1.6 mm.

As illustrated inFIG. 8, the width S1(seeFIG. 7) of the first slit811in the sub-scanning direction Y and the length LY1of the first concave mirror85in the sub-scanning direction Y are set such that light LA which has passed through the first slit811from the reading target position P1of an original document and has spread is applied to a range of the first concave mirror85in the sub-scanning direction Y. That is, light incident from an original document D is restricted in the sub-scanning direction Y, and thereby the width S1of the slit811in the first light blocking member81in the sub-scanning direction Y is set to correspond to a length which permits passing of light applied to the range of the first concave mirror85in the sub-scanning direction Y and restricts passing of light applied to portions other than the range of the first concave mirror85. That is, as illustrated inFIG. 8, an inner end portion of the slit811formed in the first light blocking member81, in the sub-scanning direction Y, is disposed at a position of blocking light which travels toward portions other than the first concave mirror85disposed to face the slit811. As illustrated inFIGS. 7 and 9, the slit811of the first light blocking member81opens in a length range allowing light to be incident to the first concave mirror array851in the main scanning direction X.

As illustrated inFIG. 8, the length LY2of the second concave mirror86in the sub-scanning direction Y is set such that parallel light LB reflected by the first concave mirror85is applied to the range of the second concave mirror86in the sub-scanning direction Y. The width S2(illustrated inFIG. 7) of the slit821of the second light blocking member82in the sub-scanning direction Y is set to correspond to the length allowing light LC reflected by the second concave mirror86to pass through the slit. That is, the inner end portion of the slit821formed in the second light blocking member82, in the sub-scanning direction Y, is disposed at a position of blocking light from portions other than the second concave mirror86disposed to face the slit821. As illustrated inFIGS. 7, 9, and 11, the slit821of the second light blocking member82opens in a length range allowing light reflected by the second concave mirror array861in the main scanning direction X to be imaged in the sensor array572.

As illustrated inFIG. 9, the length LX1of the first concave mirror85in the main scanning direction X is substantially equal to the length of the pitch of the sensor573in the main scanning direction X. The length LX2of the second concave mirror86in the main scanning direction X is substantially equal to the length of the pitch of the sensor573in the main scanning direction X. As illustrated inFIGS. 8 and 9, the first concave mirror85and the second concave mirror86are formed to cause the lengths LY1and LY2of the first concave mirror85and the second concave mirror86in the sub-scanning direction Y to be longer than the lengths LX1and LX2thereof in the main scanning direction X.

At the position of the sensor573, an image of an original document D in the sub-scanning direction Y is formed to be an inverted image, and an image of an original document D in the main scanning direction X is formed to be an erected image. In the light receiving element57constituting a line sensor, images on the adjacent sensors573are required to be joined to each other in the main scanning direction X which is a line direction of the sensor array572. Thus, an equal-magnification erected image is formed. On the contrary, the type regarding the sub-scanning direction Y (movement direction) is not limited, and thus an equal-magnification inverted image is formed. The imaging optical mechanism56is not an axisymmetric optical system but a Z-type optical system in the sub-scanning direction Y. Thus, generally, an optical design thereof is difficult. On the contrary, in the embodiment, an inverted image is formed in the sub-scanning direction Y, and curvatures of the concave mirrors85and86in the sub-scanning direction Y are set to be small. Therefore, it is possible to reduce aberration and it is easy to design the imaging optical mechanism56.

As illustrated inFIG. 9, the width of the slits831and841in the plurality of aperture members83and84in the main scanning direction X is set such that light LA incident to the optical axis direction Z1from the reading target position P1of an original document D passes through the one corresponding set of plurality of slits831and841and is applied in a range of the width of the first concave mirror85in the main scanning direction X, and stray light out of the range of the width is blocked. As illustrated inFIG. 9, for example, light which has passed through the slit811of the first light blocking member81and has been incident among rays of scattered light from the reading target position P1and is indicated by a one-dot chain line inFIG. 9is blocked by portions of the plurality of aperture members83and84other than the slits831and841. Even if the light passes through the slits831and841and then is reflected by the first concave mirror85, the reflected stray light is blocked by portions of the aperture members83and84other than the slits831and841. Therefore, finally, stray light which passes through the slit821of the second light blocking member82and then reaches the sensor573corresponding to another unit imaging element SL is hardly provided.

As illustrated inFIG. 8, the first concave mirror85has a first concave surface85A formed by a concave surface having a first curvature C1allowing light which has been widely incident from an original document D to be reflected as parallel light LB in the sub-scanning direction Y. As illustrated inFIG. 9, the first concave mirror85has a second concave surface85B formed by a concave surface having a second curvature C2allowing light LA which has been widely incident from an original document D to be reflected by the first concave mirror85and allowing the reflected light LB to be reflected in the main scanning direction X such that the light LB is imaged at a condensing position P3positioned in the middle between the first concave mirror85and the second concave mirror86, as illustrated inFIG. 10. Here, the first concave surface85A illustrated inFIG. 8indicates a concave surface shape of a section obtained by taking the first concave mirror85along a virtual surface orthogonal to the main scanning direction X. The second concave surface85B illustrated inFIGS. 9 and 10indicates a concave surface shape of a section obtained by taking the first concave mirror85along a virtual surface orthogonal to the sub-scanning direction Y.

As illustrated inFIG. 8, the second concave mirror86has a third concave surface86A formed by a concave surface having a third curvature C3. The third curvature C3allows parallel light LB which has been reflected by the first concave mirror85and then incident thereto in the sub-scanning direction Y to be reflected such that the light LB is imaged at a position P2of the sensor573. As illustrated inFIG. 11, the second concave mirror86has a fourth concave surface86B formed by a concave surface having a fourth curvature C4. The fourth curvature C4allows light LB which has been imaged at the condensing position P3between the second concave mirror86and the first concave mirror85and then incident thereto in the main scanning direction X (intersection direction) to be reflected such that the light LB is imaged at the imaging position P2of the sensor573. Here, the third concave surface86A indicates a concave surface shape of a section obtained by taking the second concave mirror86along a virtual surface orthogonal to the main scanning direction X. The fourth concave surface86B indicates a concave surface shape of a section obtained by taking the second concave mirror86along a virtual surface orthogonal to the sub-scanning direction Y.

The smallest thickness of a partition wall portion corresponding to a portion of the adjacent gap between the slits831(the slits841) in the aperture members83and84, in the main scanning direction X, is determined to have a predetermined value so as to secure a limit on molding and required strength. If the pitches of the slits831and841are large, the opening width in the main scanning direction X can be widened, and thus a bright image is obtained. However, a field depth and a focal depth become shallow, and unevenness in the quantity of light occurs largely, and thus stray light is generated. Therefore, if the pitch is reduced as small as possible, that is, set to have a value, for example, in a range of 1.0 mm to 2.6 mm, the field depth and the focal depth become deep, and a high resolution is obtained. Therefore, even though, for example, the reading surface Dp is slightly shifted in the optical axis direction Z1by an original document D slightly floating from the glass plate40, it is possible to reduce blurring of an image small, and to secure the required high resolution.

If the thickness of the partition wall portions of the aperture members83and84in the main scanning direction X is subtracted from the dimension of the pitch, the resultant corresponds to a dimension of an opening of the slits831and841in the main scanning direction X. The thickness of the partition wall portion in the main scanning direction X is about 0.4 mm in minimum from limits on molding and has a value in a range of 0.4 mm to 0.6 mm as an example. The width of the partition wall portion may be 0.2 mm or 0.3 mm so long as such a partition wall portion can be manufactured, and the required strength is obtained. However, stray light is generated, and ghost occurs in an image. As described above, the opening width of the slits831and841in the main scanning direction X is equal to or smaller than the pitch width by reason of limits on the minimum thickness of the partition wall portion, the required field depth and focal depth, and suppression of stray light. As an example, the opening width thereof has a value in a range of 0.4 mm to 2.0 mm. The thickness of the aperture members83and84in the optical axis direction Z1has a value, for example, in a range of 1.0 mm to 2.0 mm, and may be 1.5 mm as an example. If the aperture members are thick, a large quantity of stray light is generated by reflection on the inner walls of the aperture members83and84. If the aperture members are thin, it is not possible to block stray light only by the front and rear aperture members83and84.

If the pitches of the slits831and841are reduced, the total number of the slits increases. However, since it is necessary that the minimum thickness of the partition wall portions of the aperture members83and84is secured, the proportion of the partition wall portion in the main scanning direction X increases. As a result, the proportion of the slits831or841decreases. This causes an image formed in the sensor573to become dark. In addition, since the total area of the inner walls of the aperture members83and84increases, the quantity of stray light also increases.

Therefore, the brightness of an image is supplemented by widening the opening width of the slits831and841in the sub-scanning direction Y and lengthening the lengths LY1and LY2of the first concave mirror85and the second concave mirror86in the sub-scanning direction Y The lengths LY1and LY2of the first concave mirror85and the second concave mirror86in the sub-scanning direction Y are set to be values in a range of 2.5 mm to 4.5 mm as an example. In the embodiment, the lengths LY1and LY2are 3.6 mm as an example.

The lengths LY1and LY2of the concave mirrors85and86in the sub-scanning direction Y are long. Thus, in order to secure the field depth and the focal depth having a required depth, it is not possible to largely increase the curvatures C1and C3of the concave surfaces85A and86A of the concave mirrors85and86in the sub-scanning direction Y That is, if the curvatures C1and C3of the concave surfaces85A and86A of the concave mirrors85and86in the sub-scanning direction Y are set to be large, an image is blurred in the sub-scanning direction Y. Thus, the curvatures C1and C3are required to be small.

Therefore, imaging in the sub-scanning direction Y is performed to form an inverted image because the curvatures C1and C3of the concave surfaces85A and86A of the concave mirrors85and86in the sub-scanning direction Y can be reduced. For example, if an erected image is also formed in the sub-scanning direction Y similarly to the main scanning direction X, it is necessary that the curvatures C1and C3of the concave surfaces85A and86A of the concave mirrors85and86in the sub-scanning direction Y increase and imaging is performed in a manner that rays of light cross each other at an intermediate position between the concave mirrors85and86. In this, aberration increases, and the focal depth becomes shallow. Thus, in the embodiment, since an inverted image is formed in the sub-scanning direction Y, the field depth and the focal depth having a required depth in the sub-scanning direction Y are secured, and the aberration is suppressed small.

If, for example, a lens type such as an SLA is used, light is refracted and then condensed. Thus, chromatic aberration occurs. If the chromatic aberration occurs, a focal position varies depending on RGB rays of light, and thus it is necessary that the focal distance corresponding to the greatest common divisor in the RGB rays of light is set. Therefore, the focal depth becomes shallow in full color. On the contrary, the imaging optical mechanism56in the embodiment uses the light condensing phenomenon occurring by reflection of the concave mirrors85and86, regardless of the refractive index of a substance. Thus, the chromatic aberration does not occur. Therefore, it is possible to reduce an occurrence of the chromatic aberration in principle, in comparison to the lens type.

If the relative positions of the members81to84of the imaging optical mechanism56in the optical axis direction Z1are shifted from design positions, stray light to be incident from a unit imaging element SL is easily generated in another unit imaging element SL. Therefore, if two components PT1and PT2which have been integrally formed are assembled, it is possible to suppress an occurrence of position shift of the relative positions of the members81to84in the optical axis direction Z1and to suppress generation of stray light. Since configuring with the two components PT1and PT2which have been integrally formed is performed, various dimensions are set.

As illustrated inFIG. 8, the imaging optical mechanism56is an equal-magnification optical system. Thus, the imaging optical mechanism can be set to be axisymmetric with respect to an axis passing through an intermediate point of the center ray among rays LB of light, in the main scanning direction X (direction perpendicular to a paper surface). Therefore, the gap G1between the first light blocking member81and the first aperture member83can be equal to the gap G2between the second light blocking member82and the second aperture member84(G1=G2). The thicknesses of the plurality of aperture members83and84can also be equal to each other. The second concave mirror86causes the reflected light to be imaged at an optical distance LF2which is equal to an optical distance LF1between an original document D and the first concave mirror85. As illustrated inFIGS. 8 and 9, the first concave mirror85and the second concave mirror86can be set to have a common shape. That is, the lengths LY1and LY2in the sub-scanning direction Y are equal to each other (LY1=LY2), and the lengths LX1and LX2in the main scanning direction X are equal to each other (LX1=LX2). The first curvature C1is equal to the third curvature C3, and the second curvature C2is equal to the fourth curvature C4. As illustrated inFIG. 6, the first light blocking member81and the first aperture member83are integrally formed, and the second light blocking member82and the second aperture member84are integrally formed.

In the example illustrated inFIG. 6, the imaging optical mechanism56is configured with a first component PT1and a second component PT2. The first component PT1is configured by integrally forming the first light blocking member81, the second aperture member84, and the plate-like outer wall member87. The second component PT2is configured by integrally forming the second light blocking member82, the first aperture member83, and the plate-like outer wall member88. The first component PT1and the second component PT2are the same components having the same shape and the same size. That is, the imaging optical mechanism56is manufactured by assembling the two same components PT1and PT2. For example, the two components PT1and PT2are manufactured in a manner that metal is evaporated on a surface of a portion for forming a concave mirror so as to form the first concave mirror array851and the second concave mirror array861, in a resin-molded component obtained by injection molding with synthetic resin. Since the imaging optical mechanism56is configured by assembling the two components PT1and PT2, dimension accuracy of the gap between the first light blocking member81and the second aperture member84in the optical axis direction Z1and the gap between the second light blocking member82and the first aperture member83in the optical axis direction Z1is secured. Therefore, it is possible to perform positioning of the relative positions of the four members81to84arranged in the optical axis direction Z1, in the optical axis direction Z1with high accuracy.FIG. 6illustrates an example of manufacturing the imaging optical mechanism56. The members81to84and the outer wall members87and88may be separate components. The first light blocking member81and the outer wall member87may be integrally formed, the second light blocking member82and the outer wall member88may be integrally formed, and each of the aperture members83and84may be an individual component.

Then, a reading resolution of the reading module50including the imaging optical mechanism56in the embodiment is evaluated. An array pitch which is the pitches of the slits831and841and the concave mirrors85and86in the main scanning direction X in the imaging optical mechanism56is 1.6 mm. The widths S1and S2of the slits811and821in the main scanning direction X are 0.7 mm. The lengths LX1and LX2of the concave mirrors85and86in the main scanning direction X are 1.6 mm. The lengths LY1and LY2thereof in the sub-scanning direction Y is 3.6 mm. For an evaluation simulation, the product name “Code V” manufactured by Synopsis Inc. is used as lens design software.

FIG. 12illustrates a modulated transfer function curve (MTF curve) for evaluating resolution characteristics of the imaging optical mechanism56. The MTF curve is used for evaluating whether an image on an image-capturing surface of the sensor573reliably reproduces the reading target, with frequency characteristics. In the graph inFIG. 12, a horizontal axis indicates a spatial frequency (cycle/mm), and a vertical axis indicates contrast (Modulation). The spatial frequency is indicated by the number of black and white patterns per 1 mm on the image-capturing surface. The contrast is indicated by Modulation=(Lmax−Lmin)/(Lmax+Lmin) using the maximum luminance Lmax and the minimum luminance Lmin. The MTF curve is an index indicating the resolution.

The imaging optical mechanism56is configured in a manner that the plurality of unit imaging elements SL is arranged in the main scanning direction X. The unit imaging elements SL are arranged at an array pitch of 1.6 mm, and form an image of a real field of a 1.6 mm square at the reading target position P1of an original document D, on the image-capturing surface of the sensor573at the equal magnification. Therefore, the real field is in a range of 1.6 mm in the main scanning direction X.FIG. 12illustrates the contrast with respect to the spatial frequency, at positions spaced from the center of the real field at a distance of 0 mm, 0.4 mm, and 0.8 mm in the main scanning direction X. In the graph inFIG. 12, curves F1X and F1Y indicate MTF curves at the position spaced from the center of the real field at a distance of 0 mm. Curves F2X and F2Y indicate MTF curves at the position spaced from the center of the real field at a distance of 0.4 mm. Curves F3X and F3Y indicate MTF curves at the position spaced from the center of the real field at a distance of 0.8 mm. The curves F1X, F2X, and F3X indicate MTF curves in the main scanning direction X. The curves F1Y, F2Y, and F3Y indicate MTF curves in the sub-scanning direction Y. It is understood that, as the curvature becomes smaller, the resolution (curve indicated by a broken line) in the sub-scanning direction Y increases.

In the graph inFIG. 12, the minimum contrast performance of permittable image quality is obtained when the contrast is about 0.2. If the contrast more than 0.3 is obtained, the required resolution is obtained. In the scanner device31in the multifunction device11in the embodiment, the reading resolution of 6 cycles/mm is required. As understood from the graph inFIG. 12, in a spatial frequency of 6 cycles/mm, the high contrast which is equal to or more than 0.87 is obtained at all positions in a range of 0 mm to 0.8 mm in the main scanning direction X and the sub-scanning direction Y in the real field. In the spatial frequency of 12 cycles/mm, the contrast more than 0.63 is obtained in the main scanning direction X and the sub-scanning direction Y. In the spatial frequency of 16 cycles/mm, the relatively high contrast which is equal to or more than 0.42 is obtained in the main scanning direction X and the sub-scanning direction Y. As a result, the resolution of 6 to 12 cycles/mm as the spatial frequency is obtained by the reading module50including the imaging optical mechanism56. Thus, the resolution required for the scanner device31is sufficiently obtained.

Then, with the reading module50in the embodiment, an image formed on the image-capturing surface of the sensor573when an original document D has been read is recognized.FIG. 13illustrates an image formed on the image-capturing surface of the sensor573by the reading module50, when stripes of 6 cycles/mm, which has been inclined at 45 degrees as an image of an original document D has been read. The array pitch of the imaging optical mechanism56is 0.8 mm.FIG. 13illustrates an image of a range of a distance of ±0.6 mm from the center in the main scanning direction X and a range of a distance of ±0.2 mm from the center in the sub-scanning direction Y. Joint with the adjacent unit imaging element SL is shown at the position of ±0.4 mm in the main scanning direction X. As illustrated inFIG. 13, it is possible to recognize that an original document D is also read at a required resolution in the joint of the unit imaging element SL.

Regarding the reading module50including the imaging optical mechanism56in the example, the brightness and the focal depth of an image formed in the sensor573are evaluated. In the imaging optical mechanism56in the example, six types in total are provided, that is, the lengths LY1and LY2of the concave mirrors85and86in the sub-scanning direction Y are set to be two types of 3.6 mm and 4.8 mm, and array pitches of 1.4 mm, 1.6 mm, and 1.8 mm are set. As a lens array type imaging optical system, a SELFOC (registered trademark) lens array (SLA) for a copying machine is used as a comparative example. As the SLA in the comparative example, “SLA-12E” (product name) manufactured by Nippon Sheet Glass Co., Ltd. is used.

If the lengths LY1and LY2of the concave mirrors85and86in the sub-scanning direction Y are described as a concave mirror length LY,FIG. 14illustrates evaluation results in a case where the concave mirror length LY is 3.6 mm.FIG. 15illustrates evaluation results in a case where the concave mirror length LY is 4.8 mm. A brightness ratio represents a ratio of brightness in a case where brightness of an image obtained in the SLA in the comparative example has been set to 1.0, under a condition in which brightness of the linear light source52is constant. A focal depth represents a main scanning focal depth which is the focal depth in the main scanning direction X and a sub-scanning focal depth which is the focal depth in the sub-scanning direction Y.

As illustrated inFIGS. 14 and 15, the brightness ratio is smaller than that in the SLA in the comparative example, at any pitch of 1.4 mm, 1.6 mm, and 1.8 mm regardless of the concave mirror length LY of 3.6 mm and 4.8 mm. The brightness ratio is about 0.33 to 0.68. As the concave mirror length LY becomes longer, and the pitch dimension becomes larger, the higher brightness ratio is obtained. In a case where the concave mirror length LY is 3.6 mm as illustrated inFIG. 14, the brightness ratio in the example is 0.33 when the pitch is 1.4 mm, is 0.38 when the pitch is 1.6 mm, and is 0.5 when the pitch is 1.8 mm. In a case where the concave mirror length LY is 4.8 mm as illustrated inFIG. 15, the brightness ratio in the example is 0.43 when the pitch is 1.4 mm, is 0.5 when the pitch is 1.6 mm, and is 0.68 when the pitch is 1.8 mm.

Regarding the focal depth, in the SLA in the comparative example, the main scanning focal depth is 0.58 mm and shallow, and the sub-scanning focal depth is equal to or greater than 2 mm and deep. On the contrary, in any example, a difference between the main scanning focal depth and the sub-scanning focal depth is small. As illustrated inFIG. 14, in the example in which the concave mirror length LY is 3.6 mm, the main scanning focal depth gradually becomes shallow as the pitch increases, and thus has a value in a range of 0.8 mm to 1.2 mm. The sub-scanning focal depth is about 1.15 mm regardless of the pitch. As illustrated inFIG. 15, in the example in which the concave mirror length LY is 4.8 mm, the main scanning focal depth gradually becomes shallow as the pitch increases, and thus has a value in a range of 0.75 mm to 1.05 mm. The sub-scanning focal depth is about 0.7 mm regardless of the pitch.

In the example as described above, the brightness is about ½ to ⅔ of that in the SLA in the comparative example. As the concave mirror length LY becomes longer, the brightness tends to increase, but the focal depth tends to become shallow. In the example, in a case where the concave mirror length LY is 3.6 mm and 4.8 mm, and the pitch is in a range of 1.4 mm to 1.8 mm, the brightness is worse than that in the SLA, but, the focal depth which is deeper than that in the SLA, in particular, in the main scanning direction X is obtained. In the example, in particular, in a case where the concave mirror length LY is 3.6 mm, the focal depths in the main scanning direction X and the sub-scanning direction Y, which are equal to or greater than 1.0 mm are obtained at the pitch of 1.4 mm and 1.6 mm.

If the concave mirror length LY is greater than 4.8 mm, the focal depth becomes shallower than that in the SLA in the comparative example. Thus, the concave mirror length LY is preferably smaller than 4.8 mm. If the concave mirror length LY is smaller than 2.0 mm, an image becomes dark. Thus, the concave mirror length LY is preferably equal to or greater than 2.0 mm. Thus, the concave mirror length LY preferably has a value in a range of 2.0 mm to 4.8 mm.

In the imaging optical mechanism56in the example, an effect of the anti-reflection treatment is evaluated. An imaging optical mechanism90including a light blocking partition plate95illustrated inFIG. 16is used as a comparative example. As illustrated inFIG. 16, the imaging optical mechanism90in the comparative example includes a plurality of unit imaging elements SL1in the main scanning direction X. Each of the unit imaging elements SL1includes one set of light blocking members91and92and one set of concave mirrors93and94. The light blocking members91and92face each other in the optical axis direction Z1, and the concave mirrors93and94also face each other in the optical axis direction Z1. Light blocking partition plates95are arranged at a predetermined pitch on both sides of each of the unit imaging element SL1in the main scanning direction X, in the main scanning direction X.

The anti-reflection treatment for suppressing regular reflected light by scattering light reflected by the surface is performed on the inner wall surfaces of the first light blocking member81and the second light blocking member82and the wall surfaces of the aperture members83and84, in the example. In the comparative example, the anti-reflection treatment is performed on the inner wall surfaces of the light blocking members91and92and the wall surface of the light blocking partition plate95. A black alumite treated surface is used as the anti-reflection treated surface, and is compared with an ideal light absorbing surface, an ideal white scattering surface, and an ideal mirror surface. The effect of the anti-reflection treatment is evaluated with the quantity (milliwatt/square millimeter) of received light per a unit area of the sensor573in the example and the comparative example.

FIG. 17illustrates evaluation results of the anti-reflection treatment in the comparative example.FIG. 18illustrates evaluation results of the anti-reflection treatment in the example. An original document in which a fringe region of 6 line pairs/mm has been printed at the position of 8 mm in the sub-scanning direction Y, and the background is black is disposed. Then, the quantity of light received by the sensor array is evaluated. In the graphs inFIGS. 17 and 18, a horizontal axis indicates the quantity of received light, and a vertical axis indicates an original document position in the sub-scanning direction Y. In both the comparative example illustrated inFIG. 17and the example illustrated inFIG. 18, regarding the black alumite treated surface, an anti-reflection effect of light, which is substantially equal to that of the light absorbing surface is obtained. Regarding the white scattering surface, it is observed that slight light is received even at positions other than the fringe region. Thus, it is understood that the anti-reflection effect is low. Regarding the mirror surface, in the comparative example illustrated inFIG. 17, it is observed that light is received at the positions other than the fringe region of the original document and in the entirety of the fringe region. Thus, recognition of the fringe has difficulty. Regarding the mirror surface, in the example illustrated inFIG. 18, it is also observed that light is received at the positions other than the fringe region of the original document and in the fringe region. However, the quantity of received light is smaller than that in the comparative example, and the quantity of light received at the position of the black portion for the fringe in the fringe region is approximate to 0 (zero). Thus, the fringe of which recognition has not been possible in the comparative example can be recognized.

Thus, it is understood that the high anti-reflection effect is obtained in the black alumite treated surface. Regarding the mirror surface for an acceleration evaluation, the anti-reflection effect in the example is not deteriorated as much as that in the comparative example. For this reason, it is understood that a stray-light suppression effect obtained by the aperture members83and84is higher than that obtained by the light blocking partition plate95. In a case where a sand blasting treated surface is also evaluated as the anti-reflection treatment, in addition to a black treated surface such as the black alumite treated surface, the high anti-reflection effect is obtained. In a case where the sand blasting treatment is performed, synthetic resin may have any color, but the synthetic resin preferably has a color other than the white color. For example, it is more preferable that the light blocking members81and82and the aperture members83and84have been formed with black synthetic resin, and then the sand blasting treatment be performed on the surfaces thereof. The above descriptions may be applied to a matting coating treatment.

As other measures for stray light, as illustrated inFIG. 19, an aperture member89is added. In the example inFIG. 19, the third aperture member89is added between the first aperture member83and the second aperture member84in the optical axis direction Z1. The third aperture member89includes a plurality of slits891opening at a predetermined pitch in the main scanning direction X. As illustrated inFIG. 19, stray light LM is blocked by the aperture member89which has been added and is illustrated inFIG. 19. Therefore, it is possible to form an image in the sensor573at high contrast. If the number of aperture members increases, an effect for handling stray light is improved, but an image formed in the sensor573becomes dark. Thus, from a viewpoint of an effect of blocking stray light and securing brightness, it is preferable that the number of aperture members83,84, and89be as small as possible, in a range in which stray light can be suppressed to the required extent.

Next, an action of the scanner device31in the multifunction device11will be described. If a user performs an instruction to perform scanning by causing the host device to operate an operation unit such as a keyboard or a mouse, the multifunction device11receives a scanning job through a communication from the host device. If the user performs an instruction to perform scanning by operating the operation unit15, the multifunction device11receives a scanning job. If the user performs an instruction to perform copying of an original document D by operating the operation unit15, the multifunction device11receives a scanning job and a printing job. The control unit100controls driving of the scanner device31based on the scanning job, and thus causes the scanner device31to perform a reading operation of an original document D.

The control unit100performs a reading operation in the ADF mode when detecting that an original document D is provided in the set tray36, and performs the reading operation in the FB mode when detecting that the original document D is placed on the glass plate40A of the document stand33. In the ADF mode, the control unit100moves the carriage61to the reading position indicated by a solid line inFIG. 3, and drives the document transporting unit35to transport the original document D. The control unit causes the reading module50to read the original document D in the middle of being transported, through the glass plate40B. In the FB mode, the control unit100causes the carriage61to perform one reciprocation motion from the standby position in the sub-scanning direction Y. The control unit causes the reading module50to read the original document D on the document stand33through the glass plate40A while moving the carriage in the forward direction Y1.

The control unit100performs predetermined processing including shading correction and the like, on reading data obtained by reading, and thereby image data is generated. When an instruction to perform scanning has been performed, the image data is output from the multifunction device11to the host device. When an instruction to perform copying has been performed, the printing device21performs printing of an image based on the image data, and thus a medium P after copying-printing is discharged from the discharge port21A to the stacker18.

Here, in the reading module50, the original document D is read as will be described below. As illustrated inFIG. 8, scattered light reflected at the reading target position P1of the original document D passes through the slit811of the first light blocking member81, and then is incident into the imaging optical mechanism56. At this time, light incident by passing through the slit811of the first light blocking member81is restricted in the sub-scanning direction Y. Among rays of the incident light, light LA passing through the slits831and841of the plurality of aperture members83and84is reflected by the first concave mirror85in a unit imaging element SL positioned to face the reading target position P1.

As illustrated inFIG. 10, when light is reflected toward the second concave mirror86by the first concave mirror85, the light is reflected so as to form an erected image in the main scanning direction X and to be condensed at the condensing position P3being an intermediate position between the first concave mirror85and the second concave mirror86. Light LB as illustrated inFIG. 8is reflected so as to be parallel light, in the sub-scanning direction Y which is orthogonal to the main scanning direction X. In this manner, light from the reading target position P1is sequentially reflected by the corresponding first concave mirror85and second concave mirror86. Light LC reflected by the second concave mirror86is condensed at the imaging position P2of the corresponding sensor573in the sensor array572so as to form an image. At this time, as illustrated inFIGS. 8 and 9, the first concave mirror85and the second concave mirror86have the lengths LY1and LY2in the sub-scanning direction Y, which are longer than the lengths LX1and LX2in the main scanning direction X. Thus, it is possible to secure the relatively large quantity of light LA and LB allowed to be reflected. As illustrated inFIG. 8, stray light traveling toward another unit imaging element SL among rays of light which have been widely incident from the reading target position P1is blocked by portions of the two aperture members83and84other than the slits831and841. That is, stray light which has passed through the slit811from positions other than the reading target position P1of the original document D and then has been incident is blocked by the portions of the two aperture members83and84other than the slits831and841. Thus, the occurrence of a situation in which the stray light passes through the unit imaging element SL corresponding to the reading target position P1and then reaches the corresponding sensor573. As a result, an image is formed in the sensor573at high contrast.

As illustrated inFIG. 8, light LB between the first concave mirror85and the second concave mirror86in the sub-scanning direction Y becomes parallel light, and forms an inverted image in the sensor573. Since the curvatures C1and C3of the concave mirrors85and86in the sub-scanning direction Y are set to be small so as to form an inverted image in the sub-scanning direction Y, it is possible to increase the quantity of light by increasing the lengths LY1and LY2thereof in the sub-scanning direction Y and to reduce the aberration in the sub-scanning direction Y. In the main scanning direction X, an erected image is formed in the sensor573. Images formed in the adjacent concave mirrors among the concave mirrors85and86constituting the concave mirror arrays851and861overlap each other, and thus a consecutive image is obtained.

An image obtained by projecting an original document D on a mirror is formed in the sensor array572. Therefore, the control unit100performs image processing of inverting a reading image in the sub-scanning direction Y, on a pixel signal input from the sensor array572, and thereby generates image data. In this manner, it is possible to obtain image data which has been obtained by reading the original document D and has a high resolution. The total length LZ of the imaging optical mechanism56in the optical axis direction Z1is about 20 mm, and is a little larger than that in the lens type imaging optical system. However, it is possible to secure a long optical path length with respect to the dimension of the total length LZ, and to deepen the field depth and the focal depth. Therefore, even though the original document D slightly floats from the glass plate40, an occurrence of blurring of an image formed in the sensor573is difficult, and it is possible to read the original document D at the required resolution.

As illustrated inFIG. 6, in a case where the configuration is made by assembling the two components PT1and PT2, it is possible to improve position accuracy of the members81to84, to reliably suppress stray light, and to read an original document D at high contrast and a high resolution. In the imaging optical mechanism90including the light blocking partition plate95illustrated inFIG. 16, forming the light blocking partition plate95configured with a thin plate has a difficulty in manufacturing. On the contrary, the imaging optical mechanism56in the embodiment is relatively simply manufactured because the plurality of aperture members83and84configured with lattice-like plate members may be disposed.

According to the embodiment which has been described above in detail, it is possible to obtain effects as follows.

(1) The imaging optical mechanism56is mounted in the reading module50as the optical module, which moves relative to an original document D as an example of the reading target. Light incident from the original document D by reflecting light from the linear light source52as an example of the light source by the original document D is imaged in the sensor573as an example of the imaging object. The imaging optical mechanism56includes the first concave mirror85that reflects the light incident from the original document D and the second concave mirror86that is disposed at the position shifted from the first concave mirror85in the sub-scanning direction Y being the relative movement direction of the reading module50, and reflects and emits light reflected by the first concave mirror85. The imaging optical mechanism56further includes the plurality of aperture members83and84in which the slits831and841are formed along a path in which the light incident from the original document D travels toward the first concave mirror85, a path in which the light reflected by the first concave mirror85travels toward the second concave mirror86, and a path in which the light reflected by the second concave mirror86travels toward the sensor573. The first concave mirror85has the first curvature C1at which the light which has been widely incident from the original document D in the sub-scanning direction Y is reflected as parallel light LB, and the second curvature C2at which the light which has been widely incident from the original document D in the main scanning direction X is reflected so as to be imaged at the position between the first concave mirror and the second concave mirror86. The second concave mirror86has the third curvature C3at which the parallel light LB which has been reflected by the first concave mirror85and then incident in the sub-scanning direction Y is reflected so as to be imaged at the position of the sensor573, and the fourth curvature C4at which light which has been imaged at the position between the first concave mirror85and the second concave mirror and then incident in the main scanning direction X is reflected so as to be imaged at the position of the sensor573.

Thus, the light incident from the linear light source52or the light incident by reflecting the light from the linear light source52by the original document D is imaged in the sensor573through the path in which the light travels toward the first concave mirror85, the path in which the light reflected by the first concave mirror85travels toward the second concave mirror86, and the path in which the light reflected by the second concave mirror86travels toward the sensor573. At this time, only light passing through the slits831and841of the aperture members83and84in the paths is imaged in the sensor573. Therefore, stray light is blocked by the plurality of aperture members83and84, and stray light reaching the sensor573is suppressed. As a result, contrast of an image formed in the sensor573is improved, and the high resolution is obtained. Regarding the light which has been widely incident from the original document D, the light incident to portions other than the first concave mirror85in the sub-scanning direction Y is blocked by the first light blocking member81, and is reflected by the first concave mirror85in a form of, for example, parallel light without being imaged between the first concave mirror and the second concave mirror86. The light is reflected by the first concave mirror85in the main scanning direction X so as to be imaged at the position between the first concave mirror and the second concave mirror86. The parallel light which has been reflected by the first concave mirror85and then incident in the sub-scanning direction Y is reflected by the second concave mirror86, and then is imaged in the sensor573. The light which has been imaged at the position between the first concave mirror85and the second concave mirror and then incident to the second concave mirror86in the main scanning direction X is reflected by the second concave mirror86so as to be imaged at the position of the sensor573. Thus, the light from the original document D is formed as an inverted image, in the sensor573in the sub-scanning direction Y, and is formed as an erected image, in the sensor573in the main scanning direction X. In the sub-scanning direction Y, considering an overlap of an image is not required because the adjacent concave mirror is not provided. Therefore, imaging may occur slightly, and thus it is possible to secure the lengths LY1and LY2of the first concave mirror85and the second concave mirror86in the sub-scanning direction Y. Therefore, it is possible to secure the large quantity of light imaged in the sensor573, and thus to secure brightness of an image. As a result, it is possible to form an image having high contrast in the sensor573and to obtain high resolution. Since light is reflected by the first concave mirror85and the second concave mirror86, the optical path length from the original document D to the sensor573increases, and thus it is possible to increase the focal distance. Therefore, it is possible to increase a focal depth. Accordingly, it is possible to form an image of light in the sensor573at high contrast and to obtain the high resolution.

(2) In the imaging optical mechanism56, the lengths of the first concave mirror85and the second concave mirror86in the sub-scanning direction Y are longer than the lengths in the main scanning direction X. Thus, the large quantity of light can be incident and reflected to and by the first concave mirror85and the second concave mirror86. Thus, it is possible to secure brightness of an image formed in the sensor573.

(3) The imaging optical mechanism56includes the first light blocking member81having the slit811at the position facing the first concave mirror85, and the second light blocking member82having the slit821at the position facing the second concave mirror86. The first light blocking member81is disposed on a path in which the incident light travels toward the aperture member83disposed to be the closest to the incident side of light among the plurality of aperture members83and84. The second light blocking member82is disposed on a path in which the light reflected by the second concave mirror86passes through the aperture member84disposed on the closest side to the sensor573among the plurality of aperture members83and84and then travels toward the sensor573.

Thus, light which has passed through the slit811of the first light blocking member81and been incident among rays of light which has been reflected by the original document D and spread passes through the slits831and841of the plurality of aperture members83and84, and then is reflected by the first concave mirror85. Since incident light is restricted at the slit811in the sub-scanning direction Y by the first light blocking member81, it is possible to secure the large quantity of light reflected by the first concave mirror85in the sub-scanning direction Y and to reduce stray light traveling toward portions other than the first concave mirror85, in particular, stray light which is directly incident to the imaging surface from the original document D. The light reflected by the second concave mirror86passes through the slits831and841of the plurality of aperture members83and84, and passes through the slit821of the second light blocking member82, and then is imaged in the sensor573. Since the light reflected by the second concave mirror86is restricted by the slit821of the second light blocking member82in the sub-scanning direction Y, it is possible to reduce stray light in the sub-scanning direction Y in cooperation with the first light blocking member81. Thus, brightness of an image formed in the sensor573is secured, high contrast is obtained, and thus the high resolution is obtained.

(4) In the imaging optical mechanism56, the width S1of the slit811of the first light blocking member81in the sub-scanning direction Y is set to be the length as long as light incident from the original document D can be restricted to the irradiation area of the first concave mirror85in the length range in the sub-scanning direction Y. Thus, the light incident from the original document D is restricted by the slit811of the first light blocking member81in the sub-scanning direction Y, and thus it is possible to block light out of the length range of the first concave mirror85in the sub-scanning direction Y. Accordingly, it is possible to secure high contrast and to obtain the high resolution, by brightening an image of light formed in the sensor573.

(5) In the imaging optical mechanism56, the width S2of the slit821of the second light blocking member82in the sub-scanning direction Y is set to be the length as long as light reflected by the second concave mirror86can pass through the slit. Thus, all or most of rays of light other than the light reflected by the second concave mirror86are blocked by the second light blocking member82, and the light reflected by the second concave mirror86passes through the slit821in the sub-scanning direction Y. Accordingly, it is possible to secure brightness and high contrast of an image of light formed in the sensor573, and to obtain a high resolution.

(6) In the imaging optical mechanism56, the first concave mirror85and the second concave mirror86are disposed at positions which do not overlap each other in the sub-scanning direction Y and positions overlapping each other in the main scanning direction X. Thus, all or most of rays of light reflected by the first concave mirror85can be incident to the second concave mirror86, and it is possible to suppress an occurrence of a situation in which light other than the light reflected by the first concave mirror85is incident to the second concave mirror86. Accordingly, it is possible to secure brightness and high contrast of an image formed in the sensor573, and to obtain the high resolution.

(7) In the imaging optical mechanism56, an image of the original document D in the sub-scanning direction Y is formed to be an inverted image, and an image of the original document D in the main scanning direction X is formed to be an erected image, at the position of the sensor573. Thus, in a case where plural sets of first concave mirrors85, second concave mirrors86, and sensors573are arranged in the main scanning direction X, an erected image is formed in the main scanning direction X. Thus, images can be joined between the sensors573. Since an inverted image is formed in the sub-scanning direction Y, it is possible to reduce the curvatures of the first concave mirror85and the second concave mirror86in the sub-scanning direction Y and to reduce aberration.

(8) In the imaging optical mechanism56, the first light blocking member81is integrally formed with the second concave mirror86in a state of being adjacent to the second concave mirror86in the first direction in the sub-scanning direction Y. The second light blocking member82is integrally formed with the first concave mirror85in a state of being adjacent to the first concave mirror85in the second direction in the sub-scanning direction Y. Thus, it is possible to manufacture the imaging optical mechanism56with a relatively small number of components including the component obtained by integrally forming the first light blocking member81and the second concave mirror86with each other and the component obtained by integrally forming the second light blocking member82and the first concave mirror85with each other.

(9) In the imaging optical mechanism56, the second concave mirror86causes the reflected light to be imaged at an optical distance LF2which is equal to an optical distance LF1between the original document D and the first concave mirror85. Thus, the component obtained by integrally forming the first light blocking member81and the second concave mirror86with each other and the component obtained by integrally forming the second light blocking member82and the first concave mirror85with each other can be commonly used, and thus it is possible to further reduce the number of components constituting the imaging optical mechanism56.

(10) In the imaging optical mechanism56, the first concave mirror85and the second concave mirror86have a common shape. Thus, the first component PT1obtained by integrally forming the first light blocking member81and the second concave mirror86with each other and the second component PT2obtained by integrally forming the second light blocking member82and the first concave mirror85with each other can be used as common components, and thus it is possible to further reduce the number of components thereof.

(11) In the imaging optical mechanism56, the first light blocking member81and the second light blocking member82are integrally formed with the aperture members83and84. Thus, it is possible to further reduce the number of components of the imaging optical mechanism56. The arrangement position accuracy of the plurality of aperture members83and84is improved, and it is possible to reduce stray light as in the assumed design.

(12) The reading module50as an example of the optical module includes the imaging optical mechanism56, the linear light source52as an example of the light source that irradiates the original document D with light in the main scanning direction X, and the sensor array572in which the plurality of sensors573as an example of the imaging objects is arranged. The imaging optical mechanism56includes the first concave mirror array851in which the plurality of first concave mirrors85is arranged in the main scanning direction X, and the second concave mirror array861in which the plurality of second concave mirrors86is arranged in the main scanning direction X. Further, the imaging optical mechanism56includes the first light blocking member81which has the slit811opening to allow light to be incident to the first concave mirror array851, and the second light blocking member82which has the slit821opening to allow the reflected by the second concave mirror array861to be imaged in the sensor array572. Thus, it is possible to form a bright image of the original document D in the sensor array572at high contrast by the reading module50moving relative to the original document D. Accordingly, it is possible to read the original document D at a high resolution by the reading module50.

(13) In the reading module50, the slit811of the first light blocking member81opens in the length range allowing light to be incident to the first concave mirror array851in the main scanning direction X. The slit821of the second light blocking member82opens in the length range allowing light reflected by the second concave mirror array861in the main scanning direction X to be imaged in the sensor array572. Thus, the slits811and821of the first light blocking member81and the second light blocking member82open in the length range of the specular surface array in the main scanning direction X. Thus, it is possible to secure a large quantity of light incident to the imaging optical mechanism56and a large quantity of light emitted from the imaging optical mechanism56, and to secure brightness of an image formed in the sensor573, for example, in comparison to a configuration in which a plurality of slits which respectively corresponds to specular surfaces is formed.

(14) The multifunction device11as an example of an image reading apparatus includes the reading module50, the glass plate40as an example of the transparent member that defines the position of the original document D as an example of the reading target, and the transporting unit that relatively moves the original document D and the reading module50. The reading module50reads the original document D at the position on an opposite side of the original document D with the glass plate40interposed between the reading module50and the original document D, by causing the reflected light of light with which the original document D has been irradiated to be incident to the reading module. Thus, the multifunction device11can cause the reading module50to read the original document D at the high resolution.

(15) The inner end portion of the slit811formed in the first light blocking member81, in the sub-scanning direction Y, is disposed at a position of blocking light which travels toward portions other than the first concave mirror85disposed to face the slit811. The inner end portion of the slit821formed in the second light blocking member82, in the sub-scanning direction Y, is disposed at a position of blocking light from portions other than the second concave mirror86disposed to face the slit821. Thus, it is possible to reduce stray light reaching the light receiving surface of the sensor573and to secure brightness of an image while suppressing blurring of the image formed in the sensor573. Accordingly, it is possible to obtain imaging of high contrast.

Second Embodiment

Next, a second embodiment will be described with reference toFIGS. 20 and 21. In the second embodiment, a configuration for reducing stray light will be described.

As illustrated inFIG. 20, the inner end portions of the slits811and821(formed in the plurality of light blocking members81and82) in the movement direction, that is, in the sub-scanning direction Y are disposed at positions at which the light traveling toward portions other than the concave mirrors85and86as an example of the specular surfaces, which have been disposed to face each other is blocked. That is, the inner end portion of the slit811formed in the first light blocking member81, in the sub-scanning direction Y, is disposed at the position at which light traveling toward portions other than the first concave mirror85disposed to face the slit811is blocked. The inner end portion of the slit821formed in the second light blocking member82in the movement direction, that is, in the sub-scanning direction Y is disposed at the position at which the light traveling from portions other than the second concave mirror86as an example of the specular surface, which has been disposed to face the slit821is blocked. That is, the inner end portion of the slit821formed in the second light blocking member82, in the sub-scanning direction Y, is disposed at the position at which light traveling from portions other than the second concave mirror86disposed to face the slit821is blocked.

On the surface of the first light blocking member81, which opposes the first concave mirror85, the opening width of the slit811in the sub-scanning direction Y is set to a width causing the entire surface of the first concave mirror85to cover an original document line. On the surface of the second light blocking member82, which opposes the second concave mirror86, the opening width of the slit821in the sub-scanning direction Y is set to a width causing the width of the entire surface of the second concave mirror86in the sub-scanning direction Y to cover the line sensor. Further, the slits811and821of the light blocking members81and82have a shape which does not allow light to pass through the slit811of the first light blocking member81and then to pass through the second light blocking member.

As illustrated inFIG. 20, side surfaces of the slits811and821(formed in the plurality of light blocking members81and82), which have been disposed in the movement direction, that is, in the sub-scanning direction Y have inclined shapes widened toward an opposite side of the concave mirrors85and86as an example of the specular surface, which have been disposed to face each other. That is, tapered surfaces812and822having an inclined shape which has an opening widened toward the outside of the module are formed in the slits811and821of the first light blocking member81and the second light blocking member82. In detail, two surfaces facing each other in the sub-scanning direction Y among inner wall surfaces of the slit811of the first light blocking member81serve as a pair of tapered surfaces812having an opening widened toward the original document. Two surfaces facing each other in the sub-scanning direction Y among inner wall surfaces of the slit821of the second light blocking member82serve as a pair of tapered surfaces822having an opening widened toward the sensor573.

It is not necessary that the tapered surface812of the slit811, which opens toward the original document D in the first light blocking member81and the tapered surface822opening toward the sensor573in the second light blocking member82form a taper angle. However, the first light blocking member81and the second light blocking member82may be used as a common component by forming the taper angle in order to reduce cost. If the second concave mirror86is integrally formed with the first light blocking member81, and the first concave mirror85is integrally formed with the second light blocking member82, it is possible to further reduce cost of manufacturing components.

Here, from a viewpoint of suppressing an occurrence of a situation in which stray light is reflected by the tapered surface812, and thus is incident from the slit811, the taper angle between the tapered surfaces812and822may be as large as possible. If the taper angle is smaller than 20 degrees, some rays of light obtained by reflecting direct light from the original document D by the tapered surface812may be incident from the slit811and thus act as stray light. If the taper angle is too large, the light blocking members81and82become transparent, and thus transmitted light acts as stray light. Therefore, the taper angle is preferably 20 degrees or more and 60 degrees or less. In particular, in order to more reliably eliminate the above adverse effect, the taper angle is more preferably 30 degrees or more and 50 degrees or less. In the embodiment, the taper angle is set to 40 degrees as an example. The taper angle referred here means an angle of the tapered surfaces812and822to a surface parallel to both the optical axis direction Z1and the main scanning direction X. The anti-reflection treatment is performed on the surfaces of the light blocking members81and82and the aperture members83and84. Therefore, in the example, the anti-reflection treatment is also performed on the inner wall surfaces of the slits811and821, which include the tapered surfaces812and822. The surfaces of the concave mirrors85and86are not limited thereto, and preferably have high reflectance on the sufficient specular surface.

InFIG. 21, among rays of light incident from the original document D to the slit811of the first light blocking member81, light reflected by the tapered surface812which becomes wider toward an opposite side of the first concave mirror85is reflected toward the original document by the taper angle. At this time, most of rays of the reflected light are reflected from the reading position of the original document D toward a position shifted in the sub-scanning direction Y, by the taper angle. The incident light incident from the original document D through the slit811of the first light blocking member81includes direct stray light Ls which does not pass through the concave mirrors85and86but pass through the slit821of the second light blocking member82and then travels toward the sensor573, as indicated by a two-dot chain line inFIG. 21. In the embodiment, the tapered surfaces812and822have openings widened toward the original document and the sensor573, respectively. Therefore, the direct stray light Ls which travels to be the closest to the sensor573in the sub-scanning direction Y and is indicated by the two-dot chain line inFIG. 21reaches a position separated from the imaging position P2in the sub-scanning direction Y on the light receiving surface of the sensor573, in comparison to a configuration in which the slits811and821have reverse tapered surfaces widened reverse to the tapered surfaces812and822in the embodiment. For example, the direct stray light Ls reaches a position separated from the center position of the light receiving surface of the sensor573in the sub-scanning direction Y by about 1 mm. In the embodiment, the sensor573used in the CISM530is a line sensor, and the position separated from the center position of the light receiving surface of the sensor573in the sub-scanning direction Y by about 1 mm is out of the sensor573. Thus, a large influence is not applied to contrast. Thus, it is possible to suppress deterioration of contrast of a reading image due to the direct stray light Ls.FIG. 21illustrates only optical axes of light LA, LB, and LC for convenient descriptions.

As described above in detail, according to the second embodiment, it is similarly possible to obtain the effects of (1) to (15) in the first embodiment and to obtain an effect as follows.

(16) The side surfaces of the slits811and821(formed in the first light blocking member81and the second light blocking member82), which have been disposed in the sub-scanning direction Y have inclined shapes widened toward an opposite side of the concave mirrors85and86disposed to face each other. In detail, in the slits811and821, the side surfaces disposed in the sub-scanning direction Y serve as tapered surfaces812and822which have been widened toward an opposite side of the concave mirrors85and86which are respectively disposed to face the slits811and821. Therefore, it is possible to block stray light incident from the slit811of the first light blocking member81without blocking reading light from the original document D by the side surface disposed in the sub-scanning direction Y. Alternatively, it is possible to effectively separate stray light region in which it is possible that the stray light incident from the slit811reaches the light receiving surface of the sensor573, from an imaging place on the light receiving surface. Thus, it is possible to obtain imaging at high contrast.

Third Embodiment

Next, a third embodiment will be described with reference toFIGS. 22 and 23.

As illustrated inFIG. 22, extension portions813and823are formed on surfaces of the first light blocking member81and the second light blocking member82, which face each other, respectively. The extension portions813and823are provided as an example of a first light blocking portion. The extension portions813and823extend toward the concave mirrors85and86facing the slits811and821, from peripheral portions on one sides which are close to each other in the sub-scanning direction Y among both sides of the slits811and821, which interpose the openings of the slits811and821in the sub-scanning direction Y, respectively. In the embodiment, the extension portions813and823extend toward the concave mirrors85and86facing each other, from the peripheral portions of the slits811and821on one end sides close to each other in the sub-scanning direction Y with respect to the openings of the slits811and821. That is, the extension portion813is provided on the inner surface of the first light blocking member81on an opposite side of the original document. The extension portion813extends toward the first concave mirror85from an adjacent portion to the opening of the slit811, which is on the second concave mirror86side in the sub-scanning direction Y. The extension portion823is provided on the inner surface of the second light blocking member82on an opposite side of the sensor573. The extension portion823extends toward the second concave mirror86from an adjacent portion to the opening of the slit821, which is on the first concave mirror85side in the sub-scanning direction Y The extension portions813and823are formed so as not to block principal light and to have positions, shapes, and sizes of blocking direct stray light Ls (seeFIG. 23). The principal light means light LA, LB, and LC which have been reflected by the first concave mirror, reflected by the second concave mirror, have passed through the second slit821, and then reach the light receiving surface of the sensor573, among rays of incident light which has been incident from the original document D through the slit811.FIG. 23illustrates only optical axes of the light LA, LB, and LC for convenient descriptions.

The extension portion813is provided in the slit811formed in the first light blocking member81. The extension portion813is provided between a path of the light LA restricted by the slit811of the first light blocking member81and paths of the light LB incident to the second concave mirror86(as an example of the second specular surface) and the reflected light LC.

Side surfaces of the extension portions813and823in the sub-scanning direction Y as an example of the movement direction have shapes along the inner end portions of the path A of the light LA restricted by the slit811of the first light blocking member81and the paths of the light LB incident to the second concave mirror86and the reflected light LC. In the example illustrated inFIG. 22, the extension portions813and823have a shape along the optical axis direction Z1.

Positions of the extension portions813and823in the sub-scanning direction Y are positions for blocking direct stray light Ls (seeFIG. 23) as an example of light which passes through the slit811of the first light blocking member81and travels toward the slit821of the second light blocking member82. The anti-reflection treatment is performed on the surfaces of the light blocking members81and82and the aperture members83and84. Therefore, in the example, the anti-reflection treatment is also performed on the surfaces of the extension portions813and823. The surfaces of the concave mirrors85and86preferably have high reflectance on the sufficient specular surface.

InFIG. 23, the direct stray light Ls which is indicated by a two-dot chain line inFIG. 23and directly reaches the light receiving surface of the sensor573without passing through the concave mirrors85and86among rays of incident light which have been incident from the original document D into the imaging optical mechanism56is blocked by the extension portions813and823, and thus is eliminated to a level at which the light does not influence quality such as contrast at all. The extension portions813and823may formed on both sides interposing the openings of the slits811and821in the sub-scanning direction Y. In this case, the extension portions813and823may be formed to have a cylindrical shape which extends toward the concave mirrors85and86facing each other, in a state of surrounding the openings of the slits811and821. It is not essential that both the extension portions813and823are provided. Only one extension portion may be provided. Even in a case where only one of the extension portions813and823is provided, it is possible to block the direct stray light Ls as apparent fromFIG. 23.

As described above in detail, according to the second embodiment, it is similarly possible to obtain the effects of (1) to (15) in the first embodiment and to obtain an effect as follows.

(17) The extension portions813and823as an example of the first light blocking portion are provided at positions of blocking light which passes through the slit811of the first light blocking member81and then travels toward the slit821of the second light blocking member82, in at least one of the first light blocking member81and the second light blocking member82. Thus, it is possible to secure brightness of an image while blurring of the image formed in the sensor573, by reducing or eliminating direct stray light Ls. Accordingly, it is possible to obtain imaging of high contrast.

Fourth Embodiment

Next, a fourth embodiment will be described with reference toFIGS. 24to26.

As illustrated inFIG. 24, the first aperture member83and the second aperture member84include a plurality of partition walls832and842extending to portions on both sides interposing the slits831and841in the main scanning direction X, in the sub-scanning direction Y. Light blocking bars833and843as an example of a second light blocking portion are formed in the first aperture member83and the second aperture member84, respectively. The light blocking bars833and843cut across the slits831and841in the main scanning direction X, at positions at which each of the slits831and841is divided into two parts at a predetermined ratio in the sub-scanning direction Y.

As illustrated inFIG. 25, the light blocking bar833is provided between the path of light LA incident to the first concave mirror85as an example of the first specular surface and the paths of light LB incident to the second concave mirror86as an example of the second specular surface and the reflected light LC. The light blocking bar843is provided between the paths of the light LA incident to the first concave mirror85as an example of the first specular surface and the reflected light LB and the path of the light LC reflected by the second concave mirror86as an example of the second specular surface. The side surface of the light blocking bar833in the sub-scanning direction Y has a shape along the inner end portions of the path of the light LA incident to the first concave mirror85and the paths of the light LB incident to the second concave mirror86and the reflected light LC. The side surface of the light blocking bar843in the sub-scanning direction Y has a shape along the inner end portions of the paths of the light LA incident to the first concave mirror85and the reflected light LB and the path of the light LC incident to the second concave mirror86. In the example illustrated inFIG. 25, the light blocking bars833and843have a shape along the optical axis direction Z1.

Here, the shape of the side surfaces of the light blocking bars833and843, which is along the inner end portions of the paths of light on both sides interposing each of the side surfaces in the sub-scanning direction Y may be a shape in which an angle between the inner end portions of the paths of light on both the sides and the side surfaces of the light blocking bars833and843when viewed in the main scanning direction X as illustrated inFIG. 25is smaller than 45 degrees. In the fourth embodiment, inFIG. 25viewed in the main scanning direction X, the side surfaces of the light blocking bars833and843in the sub-scanning direction Y have a shape along the imaging optical mechanism56in the optical axis direction Z1. However, the side surfaces thereof may have a surface shape parallel to the inner end portion of each of the paths of light on both the sides. In short, the light blocking bars833and843can block direct stray light Ls (seeFIG. 26), and the side surfaces thereof in the sub-scanning direction Y may have a shape along the inner end portion of the paths of light on both the sides so as not to block the light LA, LB, and LC. The anti-reflection treatment is performed on the surfaces of the light blocking members81and82and the aperture members83and84. Therefore, in the example, the anti-reflection treatment is also performed on the surfaces of the light blocking bars833and843. The surfaces of the concave mirrors85and86preferably have high reflectance on the sufficient specular surface.

InFIG. 26, the direct stray light Ls which is indicated by a two-dot chain line inFIG. 26and directly reaches the light receiving surface of the sensor573through the slit821of the second light blocking member82without passing through the concave mirrors85and86among rays of incident light which have been incident from the original document D through the slit811of the first light blocking member81is blocked by the light blocking bars833and843, and thus is eliminated to a level at which the light does not influence quality such as contrast at all. The shape and the size of the light blocking bars833and843may be changed to another shape and another size of not blocking the light LA, LB, and LC but blocking the direct stray light Ls. It is not essential that both the light blocking bars833and843are provided. Only one light blocking bar may be provided.

As described above in detail, according to the fourth embodiment, it is similarly possible to obtain the effects of (1) to (15) in the first embodiment and to obtain effects as follows.

(18) The light blocking bars833and843as an example of the second light blocking portion are provided at the positions of blocking light which passes through the slit811of the first light blocking member81and then directly passes through the slit821of the second light blocking member82, in at least one of the first aperture member83and the second aperture member84. It is possible to effectively reduce or eliminate the direct stray light Ls which directly passes from the slit811of the first light blocking member81through the slit821of the second light blocking member82just by forming the light blocking bars833and843in the two aperture members83and84. Thus, it is possible to effectively eliminate the stray light region in the light receiving surfaces of the sensor573and to obtain imaging of high contrast.

Accordingly, (19) the light blocking bar833provided in the first aperture member83is positioned between the path of the light LA restricted by the slit811of the first light blocking member81and the paths of the light LB incident to the second concave mirror86and the reflected light LC. The light blocking bar843provided as an example of the second light blocking portion in the second aperture member84is positioned between the paths of the light LA incident to the first concave mirror85and the reflected light LB and the path of the light LC reflected by the second concave mirror86. Thus, it is possible to effectively reduce the direct stray light Ls without blocking the light LA, LB, and LC on the path of reflecting the first concave mirror and the second concave mirror.

(20) The side surface of the light blocking bar833in the sub-scanning direction Y has a shape along the inner end portion of each of the path of the light LA restricted by the slit811of the first light blocking member81and the paths of the light LB incident to the second concave mirror86and the reflected light LC. The side surface of the light blocking bar843in the sub-scanning direction Y has a shape along the inner end portion of each of the paths of the light LA incident to the first concave mirror85and the reflected light LB and the path of the light LC reflected by the second concave mirror86. Thus, it is possible to effectively block the direct stray light Ls, and thus to obtain imaging of high contrast.

Fifth Embodiment

Next, a fifth embodiment will be described with reference toFIGS. 27 to 29.

Some rays of light from a reading line of the original document D may be reflected by the surface (front surface) of the first aperture member83on the original document D side. The rays may be emitted from the slit811of the first light blocking member81, and then be reflected by the surface of the original document again. The reflected light may be imaged on the light receiving surface of the sensor573, from the slit811of the first light blocking member81. In the fifth embodiment, a structure in which reflected light from the front surface of the partition wall832of the first aperture member83among rays of image light abutting on the front surface of the first aperture member83is not brought back to the original document D is provided.

As illustrated inFIG. 27, a triangular prismatic protrusion834is provided on both sides interposing the slit831in the main scanning direction X, on the surface of the document stand, which faces the glass plate40in the first aperture member83. As illustrated inFIG. 28, the protrusion834has a triangular prismatic shape in which a shape viewed in the main scanning direction X is triangular. The surface of the protrusion834on an opposite side of the second concave mirror86is an inclined surface835. The inclined surface835has an angle of about 30 degrees to the surface of the first aperture member83, which opposes the original document D, from the reading line of the original document D through the slit811of the first light blocking member81. That is, the angle of the inclined surface835is about 30 degrees to the surface of the original document. The angle of the inclined surface835with the surface of the original document may have another value in a range of 20 to 50 degrees, for example. In the embodiment, the angle of the inclined surface835with the surface of the original document is set to an angle at which reflected light of light emitted from the reading line of the original document D does not travel from the slit811of the first light blocking member81toward the outside of the module, in a case where the light emitted from the original document is reflected by the inclined surface835. The angle of the inclined surface835may be appropriately changed so long as the light reflected from the slit811of the first light blocking member81by the original document D is not brought back.

If the surface of the protrusion834on the second concave mirror86side is an inclined surface, the light reflected by the inclined surface may be incident to the second concave mirror86, and act as the cause of deteriorating contrast. Thus, the above configuration is not preferable. In a region adjacent to a region of the slit831, to which the light LA is incident, in the main scanning direction X on the surface of the first aperture member83on the original document D side as the reading target, the surface on an opposite side of the second concave mirror86in the sub-scanning direction Y is set as the inclined surface835.

A protrusion having an inclined surface similar to the protrusion834may be provided in partition walls842on both sides, which interpose the slit841in the main scanning direction X, even on the surface of the second aperture member84, which is directed toward the original document D. In this case, the angle of the inclined surface of the protrusion may have any value so long as light reflected from the slit811of the first light blocking member81by the original document D is not brought back. The anti-reflection treatment is performed on the surfaces of the light blocking members81and82and the aperture members83and84. Therefore, in the example, the anti-reflection treatment is also performed on the surface of the protrusion834including the inclined surface835. The surfaces of the concave mirrors85and86preferably have high reflectance on the sufficient specular surface.

As illustrated inFIG. 29, most of rays of stray light Ls which are incident from the slit811of the first light blocking member81and then travel toward the front surface of the partition wall832of the first aperture member83are reflected by the inclined surface835. A traveling direction of the stray light Ls reflected by the inclined surface835is a direction of an opposite side of the second concave mirror86, as illustrated inFIG. 29. Therefore, the stray light Ls which is reflected by the front surface of the first aperture member83and then is brought from the slit811back to the original document D is reduced. Thus, the quantity of the stray light Ls which has been brought back to the original document D, is reflected by the surface of the original document, is incident to the slit811again, and then reaches the sensor573is significantly reduced.

As described above in detail, according to the fifth embodiment, it is similarly possible to obtain the effects of (1) to (15) in the first embodiment and to obtain an effect as follows.

(21) The inclined surface835is provided on at least a surface of the first aperture member83on the reading target side. The inclined surface835is provided in the region which is adjacent to the region of the slit831, to which light is incident, in the main scanning direction X. The inclined surface835is inclined in a direction allowing light to be reflected toward on an opposite side of the second concave mirror86in the sub-scanning direction Y as an example of the movement direction. Thus, it is possible to reduce stray light obtained in a manner that the stray light Ls which has been incident from the slit811of the first light blocking member81and then reaches the region adjacent to the slit831of the first aperture member83is brought from the slit811back to the original document D, is reflected by the surface of the original document again, is incident from the slit811, and then reaches the light receiving surface of the sensor573.

(22) Since the inclined surface835which is not parallel to the surface of the original document is formed on the surface of the partition wall832of the slit831of at least the first aperture member83among the two aperture members83and84, which opposes the original document D, it is possible to avoid an occurrence of a situation in which some rays of image light from the original document D are brought back to the original document D. Therefore, it is possible to form an image of high contrast in the sensor573even by using a glossy original document D, for example.

The above embodiments may be changed to forms as follows.Each of the first concave mirror85as an example of the first specular surface and the second concave mirror86as an example of the second specular surface may have a curvature varying in one or both of the sub-scanning direction Y as the movement direction and the main scanning direction X as the intersection direction. In short, the curvature allowing an inverted image to be formed in the sub-scanning direction Y as the movement direction and allowing an erected image to be formed in the main scanning direction X as the intersection direction may be provided.In the first concave mirror85as an example of the first specular surface and the second concave mirror86as an example of the second specular surface, one or both of the lengths LY1and LY2in the sub-scanning direction Y as the movement direction and the lengths LX1and LX2in the main scanning direction X as the intersection direction may vary. In short, the length may have any value so long as an inverted image can be formed in the sub-scanning direction Y as the movement direction, an erected image can be formed in the main scanning direction X as the intersection direction, and the second concave mirror86can totally reflect light from the first concave mirror85.An inclined angle between the first concave mirror85as an example of the first specular surface and the second concave mirror86as an example of the second specular surface may vary. In short, the inclined angle may have any value so long as an inverted image can be formed in the sub-scanning direction Y as the movement direction, and an erected image can be formed in the main scanning direction X as the intersection direction.The light reflected by the first concave mirror85as an example of the first specular surface is set to be parallel light between the first concave mirror85and the second concave mirror86in the sub-scanning direction Y as the movement direction. However, the light may be spreading light or narrowing light from the first concave mirror85toward the second concave mirror86in the sub-scanning direction Y so long as the light is not imaged at the position between the first concave mirror85and the second concave mirror86as an example of the second specular surface. In this case, in order to allow an image to be formed in the sensor573, the third curvature C3of the second concave mirror86in the sub-scanning direction Y may be changed, or the position of the sensor573may be changed. In order to secure brightness of an image formed in the imaging object, parallel light or spreading light which makes it easy to secure the length LY1of the first concave mirror85in the sub-scanning direction Y to be longer by reducing the first curvature C1is preferable. In a case where the size of the imaging optical mechanism56is reduced in a manner that the length LY1of the first concave mirror85in the sub-scanning direction Y is set to be long, and the length LY2of the second concave mirror86in the sub-scanning direction Y is set to be shorter than the length LY1, the light reflected by the first concave mirror85is preferably narrowing light from the first concave mirror85toward the second concave mirror86. With the imaging optical mechanism having any configuration, an inverted image is formed in the imaging object in the sub-scanning direction Y, and an erected image is formed in the imaging object in the main scanning direction X.The gap between the first light blocking member81and the first aperture member83may be different from the gap between the second aperture member84and the second light blocking member82. The gaps can be appropriately adjusted to allow reduction of stray light.Opening inner walls of the first aperture member83and the second aperture member84may be appropriately tapered in a concave mirror array direction (main scanning direction X). That is, the inner wall surfaces of each of the slits831and841on both sides in the array direction may be appropriately tapered. Specifically, if the inner wall surface in the first aperture member83is set to be tapered toward the original document D, the inner wall surface in the second aperture member84is set to be tapered toward the sensor573, and thus a taper angle of two degrees is provided, it is possible to reduce an occurrence of ghost. The disclosure is not limited to the above configuration and may be appropriately optimized.The width S1of the slit811of the first light blocking member81and the width S2of the slit821of the second light blocking member82may be different from each other in the sub-scanning direction Y as the movement direction. The width S1of the slit811in the sub-scanning direction Y is adjusted to have a dimension of restricting the irradiation area of light to the length range of the first concave mirror85in the sub-scanning direction Y. In addition, the width S2of the slit821in the sub-scanning direction Y is adjusted to have a dimension of allowing stray light to be reduced with respect to light which is reflected by the second concave mirror86and then is imaged in the sensor573and allowing the quantity of the light to be secured. As a result, different dimensions may be set as the widths S1and S2of the slits811and821, respectively. Since the slits811and821have a thickness in an optical path direction, light incident to the opening is scattered on an opening inner wall surface, and thus acts as stray light. In order to reduce the stray light, the opening inner wall surfaces of the slits811and821may be tapered. Specifically, one set of inner wall surfaces of the slit811in the longitudinal direction (main scanning direction X) may be tapered (widened toward the original document D) at, for example, 45 degrees. One set of inner wall surfaces of the slit821in the longitudinal direction may be tapered (widened toward the sensor573) at, for example, 45 degrees. Even though tapering is performed in a reverse direction, the effect of reducing stray light is obtained.A plurality of slits811of the first light blocking member81may be individually provided to open at positions which respectively correspond to first concave mirrors85constituting the first concave mirror array851, and a plurality of slits821of the second light blocking member82may be individually provided to open at positions which respectively correspond to second concave mirrors86constituting the second concave mirror array861. The slits811may be provided at a ratio of one for each of the plurality of concave mirrors85, in the first light blocking member81, and the slits821may be provided at a ratio of one for each of the plurality of concave mirrors86, in the second light blocking member82.The imaging optical mechanism56is disposed at a posture in which the direction perpendicular to the reading surface Dp of the reading target is set to the optical axis direction Z1. However, the imaging optical mechanism56may be disposed at an inclined posture such that a direction forming a predetermined angle with the direction perpendicular to the reading surface Dp is set to the optical axis direction Z1. In this case, a direction and an angle of inclining an optical axis can be appropriately set in a range in which scattered light obtained in a manner that regular reflected light obtained by reflecting light from the linear light source52by the reading surface Dp has not been incident to the slit811but reflected is incident.The imaging optical mechanism56may have a configuration in which an image of light obtained by causing light transmitted from the light source through the reading target to be incident is formed in the sensor573as an example of the imaging object. Examples of this type of reading target include negative films. A configuration in which light obtained by light from the light source being transmitted through the negative film is incident to the imaging optical mechanism, and the imaging optical mechanism forms an image of the incident light in the imaging object such as the sensor573may be made.In the embodiment, dimensions of the components constituting the imaging optical mechanism56, dimensions of the widths and the lengths of the gap G1to G3and the slits811,821,831, and841, the lengths LY1, LX1, LY1, and LX1of the concave mirrors85and86, and the curvatures C1to C4thereof are just examples in a case of being applied to the multifunction device11, and may be appropriately changed in accordance with, for example, a device to which the imaging optical mechanism is applied, or the required resolution.The reading module50constituting the reading element53is not limited to the CISM, and may be used in, for example, a reduction optical system.The light guide522constituting the linear light source52is not limited to the configuration illustrated inFIG. 4, and may have any configuration so long as the light guide can uniformly illuminate the original document D. The light guide may have a configuration, for example, in which a plurality of fiber wires is bundled and assembled. The linear light source52is not limited to the configuration using the luminous body521and the light guide522, and may be a linear luminous body, for example. The light source may be configured with an LED array which is generally used.The luminous body521is not limited to an LED, and a fluorescent lamp such as a xenon lamp may be used.The image reading apparatus is not limited to the multifunction device11or a copying machine including the printing device21and the scanner device31. The image reading apparatus may be a scanner device including a document transporting unit that transports an original document or may be a flat-bed type scanner device.The reading module and the imaging optical mechanism may be applied to an image reading apparatus that reads an image of a reading target other than an original document.The optical module and the imaging optical mechanism may be applied to an apparatus other than the image reading apparatus. For example, an optical module in which the imaging optical mechanism56is mounted may be applied to an apparatus provided to be movable relative to an imaging object. For example, the optical module may be applied to an optical printer. In this case, a writing module as an example of the optical module in which the imaging optical mechanism has been mounted moves relative to a photosensitive body such as a photosensitive drum as an imaging object, and then images light incident from a light source such as an organic EL element, in the photosensitive body as an imaging object. As described above, the optical module to which the imaging optical mechanism is applied is not limited to the reading module and may be a writing module that writes a light source image on an imaging object such as the photosensitive body.