Image sensor unit, image reading apparatus, and image forming apparatus

An image sensor unit includes: a plurality of sensor substrates that are connected in a main-scan direction and that are provided with sensor chips in the main-scan direction, the sensor chips converting light from an original to electric signals; and a plurality of rod-lens arrays that are connected in the main-scan direction and that are provided with a plurality of rod lenses in the main-scan direction, the rod lenses focusing the light from the original on the sensor chips, wherein connection positions between the plurality of sensor substrates are arranged at positions not overlapping with connection positions between the plurality of rod-lens arrays. A decrease in reading accuracy of an image can be reduced even if short constituent members are connected in the main-scan direction to form an elongated image sensor unit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2012-277270, filed on Dec. 19, 2012, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image sensor unit, an image reading apparatus, and an image forming apparatus. Particularly, the present invention relates to an image sensor unit, an image reading apparatus, and an image forming apparatus used to read a large original (large-sized original) and the like.

2. Description of the Related Art

Readable lengths (hereinafter, “read lengths”) of originals are generally about A4, B4, and A3 sizes in an image sensor unit used in an image reading apparatus or an image forming apparatus. In recent years, an elongated image sensor unit that can read large originals in A2, A1, and A0 sizes exceeding the read length of A3 size is used in an image reading apparatus, such as an electronic white board.

In the elongated image sensor unit, a plurality of short sensor substrates can be connected in a main-scan direction, or a plurality of short rod-lens arrays can be connected in the main-scan direction to reduce cost. Patent Document 1 discloses an image sensor including a plurality of short rod-lens arrays that are continuously arranged throughout a predetermined read length.Patent Document 1: Japanese Laid-open Patent Publication No. 2005-217630

In the image sensor unit used in an electronic white board and the like, an image to be read includes large characters, and reading accuracy is not a problem. However, in an image sensor unit or the like used to read a large map and the like, fine reading accuracy is demanded as in reading of an original in general size.

When a plurality of short sensor substrates and a plurality of short rod-lens arrays are connected to the image sensor unit that requires fine reading accuracy, the sensor substrates to be connected and the rod-lens arrays to be connected need to be accurately connected. On the other hand, even if the sensor substrates to be connected and the rod-lens arrays to be connected are connected within an acceptable connection error, there is a problem that the reading accuracy is reduced in some cases if connection positions between the sensor substrates and connection positions between the rod-lens arrays are closely arranged.

SUMMARY OF THE INVENTION

The present invention has been made in view of the foregoing problems, and an object of the present invention is to reduce a decrease in reading accuracy of an image even if a plurality of imaging element arrays are connected and a plurality of sensor substrates are connected to form an image sensor unit.

The present invention provides an image sensor unit including: a plurality of sensor substrates that are connected in a main-scan direction and that are provided with sensor chips in the main-scan direction, the sensor chips converting light from an object to be read to electric signals; and a plurality of imaging element arrays that are connected in the main-scan direction and that focus the light from the object to be read on the sensor chips, wherein connection positions between the plurality of sensor substrates are arranged at positions not overlapping with connection positions between the plurality of imaging element arrays in the main-scan direction.

The present invention provides an image reading apparatus including: an image sensor unit; and an image reading portion that reads light from an object to be read while relatively moving the image sensor unit and the object to be read, the image sensor unit including: a plurality of sensor substrates that are connected in a main-scan direction and that are provided with a plurality of sensor chips in the main-scan direction, the sensor chips converting the light from the object to be read to electric signals; and a plurality of imaging element arrays that are connected in the main-scan direction and that are provided with a plurality of imaging elements in the main-scan direction, the imaging elements focusing the light from the object to be read on the sensor chips, wherein connection positions between the plurality of sensor substrates are arranged at positions not overlapping with connection positions between the plurality of imaging element arrays in the main-scan direction.

The present invention provides an image forming apparatus including: an image sensor unit; an image reading portion that reads light from an object to be read while relatively moving the image sensor unit and the object to be read; and an image forming portion that forms an image in a recording medium, the image sensor unit including: a plurality of sensor substrates that are connected in a main-scan direction and that are provided with a plurality of sensor chips in the main-scan direction, the sensor chips converting the light from the object to be read to electric signals; and a plurality of imaging element arrays that are connected in the main-scan direction and that are provided with a plurality of imaging elements in the main-scan direction, the imaging elements focusing the light from the object to be read on the sensor chips, wherein connection positions between the plurality of sensor substrates are arranged at positions not overlapping with connection positions between the plurality of imaging element arrays in the main-scan direction.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the present embodiments, an image sensor unit described later as well as an image reading apparatus and an image forming apparatus to which the image sensor unit is applied will be described. In the image reading apparatus and the image forming apparatus, the image sensor unit emits light to an original D as an object to be read, and the image sensor unit converts light from the original D to an electric signal to read an image.

A multi-function printer (MFP) as an image reading apparatus or an image forming apparatus will be described with reference toFIG. 2.FIG. 2is a perspective view showing an appearance of an MFP10that can handle a large original. As shown inFIG. 2, the MFP10includes: an image reading portion11as image reading means for reading reflected light from the original D; and an image forming portion21as image forming means for forming (printing) an image of the original D on a roll sheet R (recording paper) as a recording medium.

The image reading portion11has a function of a so-called image scanner and is configured, for example, as follows. The image reading portion11includes a housing12, a paper feeding opening13, an original discharge opening14, an original recovery unit15, a sheet recovery unit16, an image sensor unit40, and original conveyor rollers80.

The image sensor unit40is, for example, a contact image sensor (CIS) unit. The image sensor unit40is fixed inside of the housing12.

In the image reading portion11, the original D inserted from the paper feeding opening13to the housing12is placed between the original conveyor rollers80rotated and driven by a driving mechanism and conveyed relative to the image sensor unit40at a predetermined conveyance speed. The image sensor unit40optically reads the conveyed original D, and a sensor chip51described later converts the original D to an electric signal to perform a reading operation of an image. The original D subjected to image reading is conveyed by the original conveyor rollers80and discharged from the original discharge opening14. The original recovery unit15arranged on a back surface of the housing12recovers the original D discharged from the original discharge opening14.

FIG. 3is a schematic diagram showing a structure of the image forming portion21.

The image forming portion21with a function of a so-called printer is housed in the housing12and is configured, for example, as follows. The image forming portion21includes the roll sheet R, sheet conveyor rollers22, and a printer head24. The printer head24includes, for example, ink tanks25(25c,25m,25y, and25k) with cyan C, magenta M, yellow Y, and black K inks and discharge heads26(26c,26m,26y, and26k) arranged on the ink tanks25, respectively. The image forming portion21also includes a printer head slide shaft27, a printer head drive motor28, and a belt29attached to the printer head24. As shown inFIG. 2, the image forming portion21further includes a sheet discharge opening30from which a printed sheet S is discharged.

In the image forming portion21, the sheet S as one end of the continuous roll sheet R is placed between the sheet conveyor rollers22rotated and driven by the driving mechanism and is conveyed to a printing position. The printer head drive motor28mechanically moves the belt29, and the printer head24moves in a printing direction (main-scan direction) along the printer head slide shaft27to print the image on the sheet S based on the electric signal. The operation is repeated until the printing is finished, and the printed sheet S is cut in the main-scan direction. The cut sheet S is discharged from the sheet discharge opening30by the sheet conveyor rollers22. The sheet recovery unit16arranged below the housing12recovers the sheet S discharged from the sheet discharge opening30.

Although an inkjet-type image forming apparatus has been described as the image forming portion21, the type can be any type, such as an electrophotographic type, a thermal transfer type, and a dot impact type.

A configuration of the image sensor unit40of the present invention will be described with reference to the drawings.

First Embodiment

FIG. 4is a sectional view of the image sensor unit40cut in a sub-scan direction.FIG. 5is a perspective view of constituent members of the image sensor unit40.FIG. 6is an enlarged perspective view of the constituent members of the image sensor unit40shown inFIG. 5. An image sensor unit40that can read a large (large-sized) original D in A0 size will be described here.

The image sensor unit40has an appearance of a rectangular solid. A longitudinal direction of the image sensor unit40is the main-scan direction (X direction), and the sub-scan direction (Y direction) orthogonal to the main-scan direction (X direction) is a conveyance direction of the original D.

The image sensor unit40includes: a cover glass41as a transparent member; a light source portion42; a rod-lens array portion45; a sensor substrate portion50; a frame53as a housing that houses the constituent members described above; and the like.

The cover glass41prevents dust and the like from entering the frame53. The cover glass41is planar and fixed on an upper part of the frame53.

The light source portion42illuminates the original D. As shown inFIG. 4, the light source portion42is fixed to a position below the cover glass41and adjacent to the rod-lens array portion45in the frame53. As shown inFIG. 5, the light source portion42includes light sources42a,42b, and42cused for a short image sensor unit that are arranged in a line in the main-scan direction. In the present embodiment, three light sources used for an image sensor unit with a read length of A3 size are connected and used.

As shown inFIG. 6, the light sources42ato42cinclude, for example: light emitting elements43r,43g, and43bwith wavelengths of three colors of red R, green G, and blue B; and a substrate44for mounting the light emitting elements43r,43g, and43bthat is formed long in the main-scan direction. The light emitting elements43r,43g, and43bare, for example, LED chips and are mounted in a predetermined order in the main-scan direction.

The rod-lens array portion45focuses the light (reflected light in the present embodiment) from the original D on the sensor chip51of the sensor substrate portion50. As shown inFIG. 4, the rod-lens array portion45is fixed at a position below the cover glass41and adjacent to the light source portion42in the frame53. The sensor chip51is positioned on an extension of an optical axis formed between an incident surface46and an emission surface47of the rod-lens array portion45. As shown inFIG. 5, the rod-lens array portion45includes rod-lens arrays45a,45b,45c,45d, and45eas imaging element arrays used for a short image sensor unit that are connected in a line in the main-scan direction. In the present embodiment, five rod-lens arrays used for an image sensor unit with a read length of A4 size are connected.

As shown inFIG. 6, each of the rod-lens arrays45ato45eincludes rod lenses48as a plurality of imaging elements of an erect equal magnification imaging type arranged in the main-scan direction with the optical axes being parallel, and the rod lenses48are placed between side walls49from both sides in the sub-scan direction. The rod-lens arrays45ato45eare connected by a well-known method using an adhesive or the like in the frame53. In some cases, the rod-lens arrays45ato45eare connected by being displaced in the sub-scan direction and the like within a range of an acceptable connection error.

The sensor substrate portion50converts the reflected light focused by the rod-lens array portion45to an electric signal. As shown inFIG. 4, the sensor substrate portion50is fixed to a lower end of the frame53by thermal caulking or the like. As shown inFIG. 5, the sensor substrate portion50includes sensor substrates50a,50b, and50cused for a short image sensor unit that are connected in a line in the main-scan direction. In the present embodiment, three sensor substrates used for an image sensor unit with a read length of A3 size are connected.

As shown inFIG. 6, each of the sensor substrates50ato50cincludes a plurality of sensor chips51and a substrate52on which the plurality of sensor chips51are mounted in the main-scan direction. The sensor substrates50ato50care connected by a well-known method using screws or the like. In some cases, the sensor substrates50ato50care connected by being displaced in the sub-scan direction and the like within a range of an acceptable connection error.

The frame53houses the constituent members of the image sensor unit40. As shown inFIG. 4, a plurality of projections and recesses are formed inside of the frame53to position and hold the constituent members of the image sensor unit40. As shown inFIG. 5, the frame53is formed in a rectangular solid shape that is a little longer than the read length in the main-scan direction.

Reading of the original D by the image sensor unit40with the configuration will be described. As shown inFIG. 4, the image sensor unit40successively activates the light emitting elements43r,43g, and43bof the light source portion42to emit light to the original D conveyed by the original conveyor rollers80in the sub-scan direction at a predetermined conveyance speed. The light emitted from the light source portion42uniformly illuminates the reading surface of the original D throughout the main-scan direction. The original D reflects the emitted light, and the light is focused on the sensor chip51through the rod-lens array portion45. The sensor chip51converts the focused reflected light to an electric signal, and the image sensor unit40can read the image of the original D.

The image sensor unit40reads the reflected light of one scan line, and the reading operation of one scan line in the main-scan direction of the original D is completed. After the completion of the reading operation of one scan line, reading operation of the next scan line is performed in the same way as the operation described above, along with relative movement of the original D in the sub-scan direction. In this way, the image sensor unit40repeats the reading operation of one scan line while moving in the sub-scan direction to thereby successively scan the entire surface of the original D to read the image.

A reduction in the reading accuracy in an image sensor unit formed by connecting a plurality of sensor substrates and connecting a plurality of rod-lens arrays will be described here.

FIG. 10is a schematic view showing an internal configuration of an image sensor unit100according to a comparative example. A light source portion101, a rod-lens array portion104, and a sensor substrate portion106are arranged inside of the image sensor unit100. The image sensor unit100relatively moves in the sub-scan direction (Y direction) of the original D.

The light source portion101includes a plurality of light emitting elements103mounted on a mounting surface of a substrate102formed long in the main-scan direction (X direction). The light source portion101illuminates the original D from below.

The rod-lens array portion104includes a short first rod-lens array104aand a short second rod-lens array104bconnected in the main-scan direction to be compatible with the elongated image sensor unit100. Each of the rod-lens arrays104aand104bincludes a plurality of rod lenses105of an erect equal magnification imaging type arranged in the main-scan direction. The rod-lens array portion104focuses the reflected light from the original D on a sensor chip107mounted on the sensor substrate portion106.

The sensor substrate portion106includes a short first sensor substrate106aand a short second sensor substrate106bconnected in the main-scan direction to be compatible with the elongated image sensor unit100. The sensor substrates106aand106binclude a plurality of sensor chips107(107aand107b) mounted in the main-scan direction. Each sensor chip107includes a plurality of light receiving elements108described later arranged in the main-scan direction. The sensor chip107converts the reflected light focused by the rod-lens array portion104to an electric signal. The sensor substrates106aand106bare arranged at positions that cause the sensor chips107to coincide with the optical axes of the rod lenses105in the sub-scan direction.

FIGS. 11A to 11Dare views showing examples of an arrangement relationship between the rod-lens arrays104aand104band the sensor chips107aand107bseen from an arrow A direction shown inFIG. 10. The light receiving elements108are arranged on the sensor chips107aand107b. A connection position of the first rod-lens array104aand the second rod-lens array104boverlaps with a connection position of the first sensor substrate106aand the second sensor substrate106bin the main-scan direction.

InFIG. 11A, the first rod-lens array104aand the second rod-lens array104bare accurately connected without being displaced. Since the first sensor substrate106aand the second sensor substrate106bare accurately connected, the first sensor chip107aand the second sensor chip107bare accurately arranged without being displaced. In this case, when the image sensor unit100relatively moves in the sub-scan direction to read an image of a line L in the main-scan direction drawn in the original D shown inFIG. 10, an image of a line La extending in the main-scan direction can be read as shown inFIG. 11A.

InFIG. 11B, the first rod-lens array104aand the second rod-lens array104bare accurately connected. On the other hand, since the first sensor substrate106aand the second sensor substrate106bare connected by being displaced in the sub-scan direction, the first sensor chip107aand the second sensor chip107bare displaced by G1in the sub-scan direction. In this case, when the image sensor unit100reads the image of the line L shown inFIG. 10, an image of a line Lb displaced in the sub-scan direction as shown inFIG. 11Bis read.

InFIG. 11C, since the first sensor substrate106aand the second sensor substrate106bare accurately connected, the first sensor chip107aand the second sensor chip107bare accurately arranged without being displaced. On the other hand, the first rod-lens array104aand the second rod-lens array104bare connected by being displaced by G2in the sub-scan direction. In this case, when the image sensor unit100reads the image of the line L shown inFIG. 10, an image of a line Lc displaced in the sub-scan direction as shown inFIG. 11Cis read.

InFIG. 11D, since the first sensor substrate106aand the second sensor substrate106bare connected by being displaced in the sub-scan direction, the first sensor chip107aand the second sensor chip107bare displaced by G1in the sub-scan direction. Furthermore, the first rod-lens array104aand the second rod-lens array104bare connected by being displaced by G2in the sub-scan direction. In this case, when the image sensor unit100reads the image of the line L shown inFIG. 10, an image of a line Ld significantly displaced in the sub-scan direction as shown inFIG. 11Dis read.

An amount of displacement of the displaced line Ld shown inFIG. 11Dis greater than that of the displaced line Lb shown inFIG. 11Band that of the displaced line Lc shown inFIG. 11C.

There is a problem that even if the connection error of only G1or G2as shown inFIG. 11Bor11C is an acceptable connection error, the reading accuracy of the image is significantly reduced if the connection error of G1and the connector error G2are integrated as shown inFIG. 11D.

In the present embodiment, the rod-lens array portion45includes the rod-lens arrays45ato45eused for A4 size that are connected in the main-scan direction, and the sensor substrate portion50includes the sensor substrates50ato50cused for A3 size that are connected in the main-scan direction, as described above. Therefore, the connection positions between the rod-lens arrays45ato45eand the connection positions between the sensor substrates50ato50cdo not overlap in the main-scan direction, and the connection positions can be displaced in the main-scan direction.

Specifically, the connection positions in the main-scan direction will be described with reference toFIG. 1.FIG. 1is a schematic view showing connection positions in the main-scan direction when the light source portion42, the rod-lens array portion45, and the sensor substrate portion50are attached inside of the frame53.

The light source portion42includes the light sources42ato42cused for A3 size that are connected in a line in the main-scan direction. Therefore, a connection position Pa1of the light source42aand the light source42band a connection position Pa2of the light source42band the light source42care positions that equally divide a read length M into three parts.

The rod-lens array portion45includes the rod-lens arrays45ato45eused for A4 size that are connected in a line in the main-scan direction. Therefore, a connection position Pb1of the rod-lens array45aand the rod-lens array45b, a connection position Pb2of the rod-lens array45band the rod-lens array45c, a connection position Pb3of the rod-lens array45cand the rod-lens array45d, and a connection position Pb4of the rod-lens array45dand the rod-lens array45eare positions that equally divide the read length M into five parts.

The sensor substrate portion50includes the sensor substrates50ato50cused for A3 size connected in a line in the main-scan direction. Therefore, a connection position Pc1of the sensor substrate50aand the sensor substrate50band a connection position Pc2of the sensor substrate50band the sensor substrate50care positions that equally divide the read length M into three parts.

As shown inFIG. 1, the connection positions Pb1to Pb4between the rod-lens arrays45ato45eand the connection positions Pc1and Pc2between the sensor substrates50aand50care arranged at positions not overlapped in the main-scan direction. Therefore, when the image sensor unit40reads the original D, a decrease in the reading accuracy of the image caused by the integration of the connection error between the rod-lens arrays45ato45eand the connection error between the sensor substrate50ato50ccan be reduced.

More specifically, even if the connection error between the rod-lens arrays45ato45eand the connection error between the sensor substrates50ato50care within an acceptable range, the connection errors may be integrated if the connection positions between the rod-lens arrays45ato45eand the connection positions between the sensor substrates50ato50coverlap in the main-scan direction, and the reading accuracy of the image may be reduced. In the present embodiment, since the connection positions Pb1to Pb4between the rod-lens arrays45ato45eand the connection positions Pc1and Pc2between the sensor substrates50ato50cdo not overlap in the main-scan direction, the connection error between the rod-lens arrays45ato45eand the connection error between the sensor substrates50ato50care not integrated, and the decrease in the reading accuracy of the image can be reduced.

A range W that the connection positions between the rod-lens arrays45ato45eand the connection positions between the sensor substrates50ato50care not overlapped in the main-scan direction will be described with reference toFIG. 7.FIG. 7is an enlarged view of the connection position Pb1between the rod-lens array45aand the rod-lens array45b. Here, a diameter of the rod lenses48is D. A field radius of the rod lenses48is X0, and a field diameter is 2X0. The field radius denotes a radius of an image when the rod lens48focuses the reflected light on the sensor chip51. A rod lens adjacent to the connection position Pb1in the rod-lens array45ais a rod lens48a, and a rod lens adjacent to the connection position Pb1in the rod-lens array45bis a rod lens48b.

It is assumed here that the rod-lens array45aand the rod-lens array45bhave a connection error within an acceptable range in the sub-scan direction. In this case, the reflected lights focused on the sensor chip51from the rod lens48aand the rod lens48bare displaced in the sub-scan direction in the range W where the field diameter 2X0of the rod lens48aand the field diameter 2X0of the rod lens48boverlap. If the connection position of the sensor substrate50aand the sensor substrate50bwith connection errors within the acceptable range in the sub-scan direction is arranged in the range W, the connection errors may be integrated. More specifically, the image sensor unit40reads the image of the original D as an image displaced out of the acceptable range in the sub-scan direction.

Therefore, when the sensor substrates50ato50care connected in the present embodiment, positions separated from the range W in the main-scan direction are set as the connection positions. Therefore, the integration of the connection error between the sensor substrates50ato50cand the connection error between the rod-lens arrays45ato45eare prevented, and the decrease in the reading accuracy of the image can be reduced.

If pitches between the rod lenses48shown inFIG. 7have the same dimension as the diameter D of the rod-lens arrays45ato45e,

the range W that the connection positions of the sensor substrates50ato50care not overlapped in the main-scan direction can be calculated by
W=2X0−D,
as shown inFIG. 7.

In this way, according to the present embodiment, even if the elongated image sensor unit40is formed by connecting the plurality of short rod-lens arrays45ato45eand connecting the plurality of short sensor substrates50ato50c, the decrease in the reading accuracy of the image can be reduced by arranging the connection positions between the rod-lens arrays45ato45eand the connection positions between the sensor substrates50ato50cat positions that do not overlap in the main-scan direction.

Although the image sensor unit40of A0 size has been described in the present embodiment, the arrangement is not limited to this. The size of the image sensor unit is not limited as long as an elongated image sensor unit is formed by connecting a plurality of short rod-lens arrays and connecting a plurality of short sensor substrates. Although the image sensor unit40formed by connecting five rod-lens arrays45ato45eof A4 size and connecting three sensor substrates50ato50cof A3 size has been described in the present embodiment, the arrangement is not limited to this. For example, the image sensor unit may be formed by connecting three rod-lens arrays of A3 size and connecting five sensor substrates of A4 size. Furthermore, sensor substrates of another size and rod-lens arrays of another size may be connected.

Second Embodiment

The case of forming the image sensor unit40by arranging the connection positions between the rod-lens arrays45ato45eand the connection positions between the sensor substrates50ato50cat positions that do not overlap in the main-scan direction has been described in the first embodiment. A case of also arranging a connection position between light sources62aand62bat a position not overlapping with the connection positions between the rod-lens arrays45ato45eand the connection positions between the sensor substrates50ato50cwill be described in the present embodiment.

FIG. 8Ais a perspective view showing a configuration of a light source portion62of the present embodiment. As shown inFIG. 8A, the light source portion62includes short light sources62aand62bconnected in a line in the main-scan direction at a connection position Pd that equally divides the read length M into two parts. Each of the light sources62aand62bincludes, for example: light emitting elements63r,63g, and63bwith wavelengths of three colors of red R, green G, and blue B; a substrate64for mounting the light emitting elements63r,63g, and63bthat is formed long in the main-scan direction; and a diffusion member65. The diffusion member65is attached on the substrate64to cover the light emitting elements63r,63g, and63b. The diffusion member65diffuses light emitted from the light emitting elements63r,63g, and63bto illuminate the original D.

In the light source portion62including the diffusion members65, the light diffusion may not be uniform and the light amount may be uneven near the connection position (boundary position) Pd of the light source62aand the light source62b, because the diffusion member65of the light source62aand the diffusion member65of the light source62bare divided.

Therefore, in the present embodiment, the connection position Pd between the light sources62aand62bis arranged at a position not overlapping with the connection positions between the rod-lens arrays45ato45eand the connection positions between the sensor substrates50ato50cin the main-scan direction. Here, the connection position Pd between the light sources62aand62bis a position that equally divides the read length M into two parts. As a result of the arrangement of the connection position between the light sources62aand62b, the light amount unevenness between the light sources62aand62band the connection error between the rod-lens arrays45ato45eare integrated, and the decrease in the reading quality of the image can be reduced. Similarly, the light amount unevenness between the light sources62aand62band the connection error between the sensor substrates50ato50care integrated, and the decrease in the reading quality of the image can be reduced.

Although the case that the connection position Pd between the light sources62aand62bis a position that equally divides the read length M into two parts has been described in the present embodiment, the arrangement is not limited to this. The connection position Pd between the light sources62aand62bcan be a position not overlapping with the connection positions between the rod-lens arrays45ato45eand the connection positions between the sensor substrates50ato50cin the main-scan direction, and the connection position of the light sources62aand62bis not limited. Furthermore, there can be two or more connection positions.

FIG. 8Bis a view showing a modified example with three light sources and two connection positions. InFIG. 8B, the ratio of the length of the substrate64of the light source62a, the substrate64of the light source62b, and the substrate64of the light source62cin the longitudinal direction is 1:2:1, for example. Therefore, the connection position Pd1and the connection position Pd2of the light sources62ato62care arranged at positions not overlapping with the connection positions between the rod-lens arrays45ato45eand the connection positions between the sensor substrates50ato50cin the main-scan direction.

Third Embodiment

In the present embodiment, a case of arranging a connection position between a plurality of light guides75aand75bforming a light source portion72, at a position not overlapping with the connection positions between the rod-lens array45ato45eand the connection positions between the sensor substrates50ato50cin the main-scan direction, will be described.

FIG. 9Ais a perspective view showing a configuration of the light source portion72of the present embodiment. As shown inFIG. 9A, the light source portion72includes a light emitting portion73and a light guide portion75. The light emitting portion73is, for example, an LED module including an LED chip74as a light emitting element. In the present embodiment, the light emitting portions73are arranged on both end faces of the light guide portion75. The light guide portion75is formed by connecting short light guides75aand75bin a line in the main-scan direction at a connection position Pe that equally divides the read length M into two parts. One of the both end faces of the light guide portion75in the main-scan direction is an incident surface76afor receiving light from the light emitting portion73on one end, and the other end face is an incident surface76bfor receiving light from the light emitting portion73on the other end. On a surface opposing the original D, the light guide portion75is also provided with an emission surface77for emitting the light incident on the light guide portion75to the original D. On a surface opposing the emission surface77, the light guide portion75is also provided with a diffusing surface78for reflecting and diffusing the light entered from the incident surface76aand the incident surface76b. Therefore, the light source72causes the light emitted from the light emitting portions73to enter the light guide portion75from the incident surfaces76aand76b. While the diffusing surface78reflects and diffuses the light, the light propagates through the light guide portion75, and the light is emitted from the emission surface77. In this way, the light is irradiated on the original D.

In the light source72including the connected light guide portion75, the light guide75aand the light guide75bare divided near the connection position Pe between the light guides75aand75b. Therefore, the light emitted from the emission surface77may not be uniform, and the light amount may be uneven.

In the present embodiment, the connection position Pe between the light guides75aand75bof the light source portion72is arranged at a position not overlapping with the connection positions between the rod-lens arrays45ato45eand the connection positions between the sensor substrates50ato50cin the main-scan direction. The connection position Pe between the light guides75aand75bis a position that equally divides the read length M into two parts. As a result of the arrangement of the connection position between the light guides75aand75b, the light amount unevenness between the light guides75aand75band the connection error between the rod-lens arrays45ato45eare integrated, and the decrease in the reading quality of the image can be reduced. Similarly, the light amount unevenness between the light guides75aand75band the connection error between the sensor substrates50ato50care integrated, and the decrease in the reading quality of the image can be reduced.

Although the case that the connection position Pe between the light guides75aand75bis a position that equally divides the read length M into two parts has been described in the present embodiment, the arrangement is not limited to this. The connection position Pe between the light guides75aand75bcan be a position not overlapping with the connection positions between the rod-lens array45ato45eand the connection positions between the sensor substrates50ato50cin the main-scan direction, and the connection position of the light sources62aand62bis not limited. Furthermore, there can be two or more connection positions.

FIG. 9Bis a view showing a modified example with three light guides and two connection positions. InFIG. 9B, the ratio of the length of the light guide75a, the light guide75b, and the light guide75cin the longitudinal direction is 1:2:1, for example. Therefore, a connection position Pe1and a connection position Pe2of the light guides75ato75care arranged at positions not overlapping with the connection positions between the rod-lens arrays45ato45eand the connection positions between the sensor substrates50ato50cin the main-scan direction.

A light emitting portion may be arranged on only one end, instead of arranging the light emitting portions73on both ends of the light guide portion75.

Although the embodiments are used to describe the present invention, the present invention is not limited only to the embodiments, and changes can be made within the scope of the present invention. For example, although the case of using the rod-lens array as the imaging element array has been described in the present embodiment, the arrangement is not limited to this, and a well-known lens array, such as a microlens array, can be used.

The present invention can be effectively used for an image sensor unit and for an image reading apparatus and an image forming apparatus (for example, image scanner, facsimile, copying machine, and compound machine) to which the image sensor unit is applied.

According to the present invention, a decrease in the reading accuracy of an image can be reduced even if a plurality image element arrays are connected and a plurality of sensor substrates are connected to form an image sensor unit.