Light guide member, illuminating device, and image reading apparatus and image forming apparatus using same

A light guide member includes a main body part, and an entrance surface, a strip-shaped exit surface and a strip-shaped reflecting surface that are formed on the main body part. The illumination light is output from the exit surface. The reflecting surface extends in the first direction on a face placed opposite to the exit surface of the main body part and reflects the illumination light. The reflecting surface includes, on a flat face, a reflection pattern surface provided with a plurality of minute reflective concave parts having a function of reflecting the illumination light toward the exit surface. The reflective concave parts each include a deflection surface which deflects the illumination light in a direction in which a reflection angle widens in a cross sectional view in a second direction that is orthogonal to the first direction in a horizontal direction, and then reflects the illumination light.

This application relates to and claims priority from Japanese Patent Application No. 2012-17726, filed on Jan. 31, 2012, the entire disclosure of which is incorporated herein by reference.

BACKGROUND

The present disclosure relates to a light guide member for guiding an illumination light emitted from a light source, an illuminating device using the foregoing light guide member, and an image reading apparatus and an image forming apparatus using the same.

An image forming apparatus such as a scanner or a copy machine uses an illuminating device, which irradiates light on a document sheet, in order to optically read an image of the document sheet. In recent years, a white light emitting diode (LED) is being used as the light source of the illuminating device due to its advantage of having high luminous efficiency. With this type of illuminating device, it is necessary to linearly illuminate the document sheet. Therefore, a bar-shaped light guide member and the white LED are combined to generate a linear illumination light since an LED is a point light source. The light guide member includes an entrance surface which is disposed at one end of the light guide member and through which the illumination light emitted by the white LED enters, a strip-shaped exit surface which extends in the longitudinal direction of the light guide member and outputs the illumination light therefrom, and a strip-shaped reflecting surface which is formed on a face of the light guide member, the face being placed opposite to the exit surface and which reflects the illumination light.

The illumination light that entered the entrance surface propagates within the light guide member and is output to the outside from the exit surface. This outgoing light includes an illumination light (direct light) that heads directly from the white LED to the reflecting surface and then is reflected off the reflecting surface, and an illumination light (indirect light) which heads toward the reflecting surface after being totally reflected one or more times by a peripheral surface of the light guide member and that is reflected off the reflecting surface. The direct light is mainly output from a portion near the entrance surface. Here, since the direct light and the indirect light have different illumination intensity, there is a problem in that the uniformity of the illumination light cannot be obtained in the longitudinal direction of the light guide member. In order to resolve this problem, with a conventional illuminating device, the cross section shape of the light guide member is formed in a polygonal shape, and the shape of its main scanning direction is caused to be different so that the direct light is not output from the exit surface.

Nevertheless, in order to generate an indirect light, the illumination light emitted from the white LED needs to be totally reflected at least one by the peripheral surface of the light guide member. Consequently, with the light guide member of a conventional illuminating device, a certain length of distance needs to be provided between the near ends of the entrance surface and the exit surface. This leads to the entire length of the light guide member being extended, and inhibits the miniaturization of the illuminating device.

SUMMARY

The light guide member according to one aspect of the present disclosure is a light guide member which is used by being combined with a light source that emits an illumination light, and includes a main body part, and an entrance surface, a strip-shaped exit surface and a strip-shaped reflecting surface that are formed on the main body part. The main body part has a long rod shape in a first direction and guides the illumination light. The entrance surface is one end face of the main body part and the illumination light enters therein. The exit surface extends in the first direction on a surface of the main body part and the illumination light is output therefrom. The reflecting surface extends in the first direction on a face of the main body part, the face being placed opposite to the exit surface, and reflects the illumination light. The reflecting surface includes, on a flat face, a reflection pattern surface provided with a plurality of minute reflective concave parts having a function of reflecting the illumination light toward the exit surface. The reflective concave parts each include a deflection surface which deflects the illumination light in a direction in which a reflection angle widens in a cross sectional view in a second direction that is orthogonal to the first direction in a horizontal direction, and reflects the illumination light.

The illuminating device according to another aspect of the present disclosure includes a light source which emits an illumination light, and the foregoing light guide member which is used by being combined with the light source.

The image reading apparatus according to another aspect of the present disclosure includes the foregoing illuminating device which irradiates an illumination light on a document sheet, and a light-receiving device which receives a reflected light from the document sheet and converts the reflected light into an electrical signal, wherein the first direction is a main scanning direction, and the second direction is a sub scanning direction.

The imaging forming apparatus according to yet another aspect of the present disclosure includes the foregoing image reading apparatus, and an image carrier in which an electrostatic latent image is formed on a peripheral surface thereof based on image data output from the image reading apparatus.

DETAILED DESCRIPTION

Embodiments of the present disclosure are now explained in detail with reference to the drawings.FIG. 1is a cross sectional view showing the internal structure of the image forming apparatus1according to an embodiment of the present disclosure. Here, as the image forming apparatus1, illustrated is a so-called internal discharge-type copy machine. Note that the apparatus to which the illuminating device according to the present disclosure can be applied is not limited to a copy machine, and the present disclosure can also be applied to, for example, a scanner device, a facsimile device, or a multifunction machine.

The image forming apparatus1includes a housing2having a case structure of a substantially rectangular shape and which includes an internal space (internal sheet discharge unit24). The housing2includes a lower case (apparatus body21) which houses various equipment for forming images, an upper case (image reading apparatus22) disposed above the apparatus body21, and a connecting case23which connects the apparatus body21and the image reading apparatus22. The image reading apparatus22optically reads an image of a document sheet, and generates image data according to the document image. The apparatus body21performs processing of forming a toner image on a sheet based on the image data. An internal sheet discharge unit24for discharging the sheet after image is formed thereon is provided between the apparatus body21and the image reading apparatus22. The connecting case23is disposed on the right-side face of the housing2, and is provided with a discharge outlet961for discharging the sheet to the internal sheet discharge unit24.

The apparatus body21internally houses, in order from the upper side, toner containers99Y,99M,99C,99Bk, an intermediate transfer unit92, an image forming unit93, an exposure unit94, and a sheet feed cassette211.

In order to form a full-color toner image, the image forming unit93includes four image forming units10Y,10M,10C,10Bk for forming the respective toner images of yellow (Y), magenta (M), cyan (C) and black (Bk). The respective image forming units10Y,10M,10C,10Bk include a photoconductive drum11, and a charging unit12, a developing device13, a primary transfer roller14and a cleaning device15disposed around the photoconductive drum11.

The photoconductive drum11rotates around its axis, and an electrostatic latent image and a toner image are formed on its peripheral surface. As the photoconductive drum11, used may be a photoconductive drum configured from an amorphous silicon (a-Si)-based material. The charging unit12uniformly charges the surface of the photoconductive drum11. The peripheral surface of the photoconductive drum11after the charging is exposed by the exposure unit94, and an electrostatic latent image is formed thereon.

The developing device13provides a toner to the peripheral surface of the photoconductive drum11in order to develop the electrostatic latent image formed on the photoconductive drum11. The developing device13is for use with a two-component developer, and includes agitation rollers16,17, a magnetic roller18, and a development roller19. The agitation rollers16,17charge the toner by circulating and conveying the two-component developer, while agitating the toner. A two-component developer layer is formed on the peripheral surface of the magnetic roller18, and a toner layer formed as a result of the toner being transferred between the magnetic roller18and the development roller19, via potential difference, is formed on the peripheral surface of the development roller19. The toner on the development roller19is supplied to the peripheral surface of the photoconductive drum11, and the electrostatic latent image is developed thereby.

The primary transfer roller14forms a nip portion with the photoconductive drum11across an intermediate transfer belt921provided to the intermediate transfer unit92, and transfers, as primary transfer, the toner on the photoconductive drum11onto the intermediate transfer belt921. The cleaning device15cleans the peripheral surface of the photoconductive drum11after the toner image is transferred.

A yellow toner container99Y, a magenta toner container99M, a cyan toner container99C, and a black toner container99Bk respectively store toners of the respective colors, and supply the toners of the respective colors, through a supply channel not shown, to the developing device13of the image forming units10Y,10M,10C,10Bk corresponding to the respective colors of Y, M, C, Bk.

The exposure unit94includes various optical equipment such as a light source, a polygon mirror, a reflective mirror, and a deflection mirror, and forms an electrostatic latent image by irradiating light based on image data of the document image on the peripheral surface of the photoconductive drum11provided to the respective image forming units10Y,10M,10C,10Bk.

The intermediate transfer unit92includes an intermediate transfer belt921, a drive roller922and a driven roller923. The toner image on the photoconductive drum11of the respective colors is overlaid (primary transfer) on the intermediate transfer belt921. The overlaid toner image is transferred, as secondary transfer, onto the sheet supplied from the sheet feed cassette211or the sheet feed tray30in the secondary transfer unit98. The drive roller922and the driven roller923for rotatively driving the intermediate transfer belt921are rotatably supported by the apparatus body21.

The sheet feed cassette211houses a sheet bundle in which a plurality of sheets are layered. A pickup roller212is disposed at the upper part on the right end side of the sheet feed cassette211. Based on the drive of the pickup roller212, the uppermost sheet of the sheet bundle in the sheet feed cassette211is fed one sheet at a time to the delivery path26. Note that a sheet feed unit40including a sheet feed tray30for manually feeding sheet is provided to the right side face of the apparatus body21. The sheet mounted on the sheet feed tray30is carried to the delivery path26by driving of the sheet feed roller41of the sheet feed unit40.

Provided to the downstream side of the delivery path26is a sheet path28which extends to the discharge outlet961via the secondary transfer unit98, and a fixing unit97and a sheet discharge unit96described later. The upstream part of the sheet path28is formed between an inner wall formed on the apparatus body21and an inner wall formed on the inner surface of the reverse transfer unit29. Note that the outer face of the reverse transfer unit29configures one face of a reverse path291on which the sheet is reversed and transferred during double-side printing. A resist roller pair27is disposed on a side of the sheet path28that is more upstream than the secondary transfer unit98. The sheet is once stopped at the resist roller pair27and, after being subject to skew correction, conveyed to the secondary transfer unit98at a predetermined timing for performing the image transfer.

A fixing unit97and a sheet discharge unit96are housed inside the connecting case23. The fixing unit97includes a fixing roller and a pressure roller, and fixing processing is performed by heating and pressing the sheet, to which the toner image is secondarily transferred, in the secondary transfer unit98. The sheet with the color image that is subject to the fixation processing is discharged from the discharge outlet961toward the internal sheet discharge unit24by the sheet discharge unit96disposed downstream of the fixation unit97.

The image reading apparatus22includes a first contact glass222and a second contact glass223fitted into an upper face221of the upper case. The first contact glass222is provided for use in reading the document sheet automatically fed from an automatic document feeder (ADF; not shown) when an ADF is disposed on the image reading apparatus22. The second contact glass223is provided for use in reading a hand-placed document sheet.

The image reading apparatus22includes a first moving carriage224, a second moving carriage225, a condenser lens unit228and an imaging device229(light-receiving device) housed in the upper case. Mounted on the first moving carriage224are the illuminating device50according to an embodiment of the present disclosure, and a first reflective mirror226. Mounted on the second moving carriage225are a second reflective mirror227A and a third reflective mirror227B for reversing the light path.

The first moving carriage224moves reciprocally in the left-right direction along the lower surface of the first contact glass222and the second contact glass223. The second moving carriage225reciprocally moves in the left-right direction at ½ the travel distance of the first moving carriage224. During the automatic feed mode where the document sheet is automatically fed from an automatic document feeder not shown, the first moving carriage224moves to a position immediately below the first contact glass222, and becomes stationary. In this stationary condition, light is emitted from the illuminating device50toward the document sheet. Meanwhile, during the hand-placement mode where the document sheet is manually placed on the second contact glass223, the first moving carriage224moves from a position immediately below the left end of the second contact glass223toward the right in accordance with the size of the document sheet. During this movement, light is emitted from the illuminating device50toward the document sheet. The second moving carriage225moves rightward following the first moving carriage224at ½ the travel distance of the first moving carriage224.

The illuminating device50irradiates a linear illumination light, which extends in the main scanning direction, on the document sheet. Specifically, the illuminating device50emits an illumination light for optically reading the document sheet image toward the automatically fed document sheet that passes on the first contact glass222or toward the manually placed document sheet mounted on the second contact glass223. The first reflective mirror226reflects, toward the second reflective mirror227A of the second moving carriage225, the reflected light of the illumination light that is emitted by the illuminating device50toward the document sheet.

The second reflective mirror227A reflects, toward the third reflective mirror227B, the reflected light that is reflected by the first reflective mirror226. The third reflective mirror227B reflects the reflected light toward the condenser lens unit228. The condenser lens unit228images the optical image of the reflected light, which is reflected by the third reflective mirror227B, on the imaging surface of the imaging device229. The imaging device229is configured from a charge coupled device (CCD) or the like, and photoelectrically converts the reflected light into an analog electrical signal. This analog electrical signal is converted into a digital electrical signal via an A/D conversion circuit (not shown), and thereafter input as image data into the foregoing exposure unit94.

A white reference plate (not shown) for deciding the white reference of the reading concentration is disposed on the left end side of the second contact glass223. An illumination light is irradiated on the white reference plate before the image reading operation, the reflected light thereof is received by the imaging device229, and a correction value for outputting the image data at such time uniformly in the main scanning direction is acquired in advance (shading correction).

The illuminating device50is now explained in detail.FIG. 2is a perspective view of the illuminating device50, andFIG. 3is a cross sectional view of line III-III ofFIG. 2. The illuminating device50includes a light source51for emitting an illumination light, and a light guide member52which propagates the illumination light emitted from the light source51and which converts the illumination light into a linear illumination light and outputs the linear illumination light.

The light source51has a thin discoid shape, and includes a white light emitting diode (LED)51L which emits a white light. As the white LED51L, used may be, for example, an LED package configured by sealing a GaN-based or an InGaN-based semiconductor light-emitting device which emits a blue light or a ultraviolet light into a phosphor-containing transparent resin. Note that, while one white LED51L is shown inFIG. 2, in reality a plurality of moduled white LEDs51L are provided to the light source51as shown inFIG. 7.

The light guide member52is molded from a translucent resin material, has a long rod shape in the main scanning direction (first direction), and includes a main body part53which guides the illumination light emitted from the light source51, an entrance surface54which is one end face of the main body part53and through which the illumination light enters, and a far end face55which is an end face on a side placed opposite to the entrance surface54. A light-emitting face of the foregoing light source51is in contact with the entrance surface54. The far end face55is provided with an antireflective coating layer for preventing the illumination light from leaking from the far end face55.

The light guide member52additionally includes an exit surface56disposed on the upper face side of the main body part (side that faces the first, second contact glasses222,223), and a reflecting surface57disposed on the lower face side of the main body part53in a manner of facing the exit surface56. The exit surface56is a strip-shaped face extending in the main scanning direction, and is a face that outputs the illumination light toward the first, second contact glasses222,223(document sheet). The reflecting surface57is similarly a strip-shaped face extending in the main scanning direction, and reflects, toward the exit surface56, the illumination light that is propagating in the main body part53. The exit surface56has a relatively moderate convex curved surface in the sub scanning direction. Meanwhile, the reflecting surface57is a flat face. As described in detail later, the reflecting surface57includes a reflection pattern surface58P (refer toFIG. 7) provided with a plurality of minute reflective concave parts (oval concave parts58).

FIG. 4is a diagram schematically showing the propagation state of the illumination light in the light guide member52. The illumination light enters the main body part53through the entrance surface54from the light source51. Since the light source51is a point light source, the illumination light has the characteristics of diffused light. The entered illumination light basically advances in the direction of the far end face55while repeating total reflection on the peripheral surface of the main body part53based on the refractive index difference between the constituent material of the light guide member52and air. Nevertheless, as a result of the reflecting surface57including the reflection pattern surface58P described later being provided facing the exit surface56, the illumination light is output from the exit surface56. Since the main body part53has a long bar shape in the main scanning direction, the illumination light emitted from the light guide member52becomes a linear illumination light extending in the main scanning direction.

As described above, the illumination light output from the light guide member52contains a direct light DL and an indirect light IL. The direct light DL is an illumination light L1which directly heads toward the reflecting surface57from the light source51, and is the light that is output from the exit surface56as a result of the illumination light L1being reflected off the reflecting surface57(reflection pattern surface58P). Meanwhile, the indirect light IL is an illumination light L2which heads toward the reflecting surface57after being totally reflected one or more times by the peripheral surface of the main body part53, and is the light that is output from the exit surface56as a result of the illumination light L2being reflected off the reflecting surface57. The direct light DL is mainly output from the portion near the entrance surface54on the exit surface56.

Conventionally, generally used as the reflection pattern surface formed on the reflecting surface57was a V-shaped concave groove extending in the sub scanning direction, which is a minute concave grove that functions similarly to a prism. A reflection pattern in which a plurality of such V-shaped prisms being arranged in the main scanning direction is being generally used under the present circumstances. Nevertheless, in the sub scanning direction, a V-shaped prism is characterized in reflecting, without deflecting, the angle of the light beam that entered the V-shaped prism. Accordingly, the direct light DL and the indirect light IL will have a different output optical intensity distribution in the sub scanning direction.

FIG. 5is a graph showing the angular distribution of the optical intensity, in the sub scanning direction, of the direct light DL and the indirect light IL output from the light guide member52including the reflection pattern surface of the foregoing V-shaped prism. As evident fromFIG. 5, the direct light DL has sharp characteristics comparison to the indirect light IL.FIG. 6is a diagram schematically showing the intensity distribution of the direct light DL and the indirect light IL shown in the graph ofFIG. 5by causing the intensity scale to coincide.

When viewed from the sub scanning direction, the direct light DL will hardly diffuse since the illumination light L1, which directly heads to the reflecting surface57(V-shaped prism) from the light source51at a predetermined limited incidence angle, is reflected by the V-shaped prism at the same angle. This is the reason why the intensity distribution of the direct light DL is sharp. Meanwhile, the indirect light IL is the light that is created by the illumination light L2, which has every incidence angle as a result of being totally reflected by the peripheral surface of the main body part53, being reflected off the V-shaped prism. Accordingly, the intensity distribution of the indirect light IL becomes relatively broad.

This kind of difference in the intensity distribution of the direct light DL and the indirect light IL induces a problem in that the uniformity of the illumination light cannot be obtained in the longitudinal direction of the light guide member52. This is due to the direct light DL mainly being output from the portion near the entrance surface54as described above. If the intensity distribution of the illumination light differs in the main scanning direction, the variation of the amount of reflected light from the document sheet will differ when a position gap occurs in the reading position of the document sheet or when the document sheet floats from the contact glass. This will generate unevenness in the reading concentration in the main scanning direction.

In light of the foregoing problem, the present disclosure has devised the shape of the reflection pattern formed on the reflecting surface57. This reflection pattern is formed from minute reflective concave parts formed on the flat reflecting surface57as recesses. The reflective concave parts each include a deflection surface which deflects the illumination light in a direction in which the reflection angle widens in the cross sectional view in the sub scanning direction (second direction), and then reflects the illumination light. The reflection pattern surface is formed on the reflecting surface57by a plurality of such reflective concave parts.

As a result of including this kind of reflection pattern surface, the illumination light that enters the reflective concave part is deflected in a direction in which the reflection angle widens on the deflection surface, then reflected. Thus, the reflection angle of the direct light DL in a cross sectional view of the sub scanning direction can be widened. Consequently, the characteristics of the direct light DL can be appropriated to the characteristics of the indirect light IL, and the uniformity of the illumination light output from the exit surface56in the main scanning direction can be secured. Moreover, the light guide member52can be configured in a minimal length.

A specific example of the reflecting surface57including the reflective concave part having the deflection surface is now explained.FIG. 7is a perspective view showing the vicinity of the entrance surface54of the light guide member according to this embodiment, andFIG. 8is an expanded perspective view of the reflection pattern surface58P provided to the light guide member52. Here, as an example of the reflective concave part having the foregoing deflection surface, an oval concave part58having a shape of a semi-oval body is illustrated.FIG. 9is an enlarged diagram showing one oval concave part58.

As explained previously with reference toFIG. 2, the illuminating device50includes a light source51and a light guide member52. The light-emitting surface of the light source faces and comes into contact with the entrance surface54of the light guide member52. InFIG. 7, a light source51in which six white LEDs51L are arranged in a 2×3 matrix is illustrated. The rod-shaped main body part53of the light guide member52includes an exit surface56which emits a linear illumination light toward the document sheet, and a reflecting surface57which faces the exit surface56. The reflecting surface57is a flat face, and includes a reflection pattern surface58P provided with a plurality of oval concave parts58having the function of reflecting, toward the exit surface56, the illumination light that entered the light guide member52from the light source51.

The oval concave part58is recessed from the reflecting surface57toward the inside of the main body part53so that the long diameter direction thereof extends in the sub scanning direction (second direction). As a result of a plurality of such oval concave parts58being arranged in series in a predetermined pitch in the sub scanning direction, one concave part array58L (FIG. 8; unit reflective concave part array) is formed. The reflection pattern surface58P is formed by a plurality of the concave part arrays58L being juxtaposed in a predetermined pitch in the main scanning direction.

At the portion of the concave part array58L, the illumination light is reflected toward the exit surface56. The illumination light at such time is deflected in a direction in which the reflection angle widens in a cross sectional view in the sub scanning direction. Meanwhile, a flat part58H exists between the concave part arrays58L. The flat part58H is a part that functions to totally reflect the illumination light so as to propagate the illumination light toward the far end face55(FIG. 2). Thus, the short diameter direction of the oval concave part is disposed in the main scanning direction. The reflection pattern surface58P includes a starting end positioned toward the far end face55at a predetermined length from the entrance surface54on the reflecting surface57. The position of this staring end is decided in consideration of the divergence angle of the illumination light emitted by the light source51.

The light guide member52may be obtained by using a translucent resin material, and performing injection molding of melting the resin material and injecting it into a mold. In the foregoing case, the foregoing oval concave parts58(reflection pattern surface58P) can be easily formed by providing a convex part of the semi-oval body at the portion corresponding to the reflecting surface57of the mold. In other words, the reflective concave part having a deflection function can be formed with a simple shape of a semi-oval body.

Referring toFIG. 9, the oval concave part58includes an oval opening581having a long diameter d of a predetermined length. In addition, the oval concave part58includes a semi-oval body concave curve582(deflection surface) in which the depth h (½ length of the short diameter of the oval body) from the opening581(flat face of the reflecting surface57) is the deepest part. The depth h is set to a suitable size that is preferably 100 μm or less. For example, the depth h is desirably selected from a range of 15 μm to 90 μm.

FIG. 10AandFIG. 10Bare diagrams explaining the reflection state of the illumination light based on the reflective concave part.FIG. 10Bshows the reflection state of the illumination light L based on the reflective concave part58A such as the foregoing V-shaped prism which does not have a deflecting component in the sub scanning direction. As described above, with this kind of reflective concave part58A, since the illumination light L is reflected without being deflected, the illumination light L will not diffuse in the sub scanning direction. Meanwhile, as shown inFIG. 10A, with a reflective concave part such as the oval concave part58, the illumination light L is deflected as a result of being reflected by the concave curve582, and the illumination light L will diffuse in the sub scanning direction. Thus, even in cases where the illumination light directly enters the oval concave part58from the light source51, the characteristics of the reflected light; that is, the characteristics of the direct light DL (FIG. 4) output from the exit surface56can be caused to approach the characteristics of the indirect light IL.

Here, d:h as the ratio of the long diameter d and the depth h of the oval concave part58is desirably within the range of 3:1 to 15:1. As a result of the d:h ratio being within the foregoing range, the deflection characteristics of the direct light DL can be rationalized. In particular, d:h is desirably selected from the range of 5:1 to 8:1.

FIG. 11is a graph showing the measurement result of the angular distribution of the optical intensity, in the sub scanning direction, of the illumination light output from the exit surface56in a case where the shape (foregoing d:h) of the oval concave part58is caused to differ. InFIG. 11, curved lines DL and IL correspond to the direct light DL and the indirect light IL explained previously with reference toFIG. 5. Meanwhile, curved lines S1, S2, S3and S4form the reflection pattern surface58P in which the oval concave parts58are provided to the reflecting surface57, and show the optical intensity of the direct light DL when the foregoing d:h of the oval concave parts58is set respectively as follows.

As evident fromFIG. 11, as a result of providing the reflection pattern surface58P having the oval concave parts58to the light guide member52, the sharpness of the curved lines S1, S2, S3and S4is alleviated in comparison to the conventional direct light DL, and it can be seen that the direct light DL has directional characteristics that approach the indirect light IL. In particular, the curved line S2has characteristics which are approximate to the indirect light IL. When the long diameter d is made shorter than the curved line S1, the degree of deflection increases excessively, and the tendency of the illumination light being excessively diffused becomes prominent. Meanwhile, when the long diameter d is made longer than the curved line S4, the deflecting function will deteriorate and the characteristics of the oval concave part58also approach the characteristics of a V-shaped prism. Accordingly, d:h is desirably selected from the range of 3:1 to 15:1, and, from the perspective of causing the angular distribution of the direct light DL to further approach the indirect light IL, d:h is desirably selected from the range of 5:1 to 8:1.

According to the illuminating device50of this embodiment explained above, the characteristics of the direct light DL reflected off the reflecting surface57can be caused to approximate the characteristics of the indirect light IL. In other words, difference in the intensity distribution of the direct light DL and the indirect light IL as shown in the example ofFIG. 6will not arise, and the direct light DL and the indirect light IL will substantially have the same intensity distribution. Accordingly, a uniform linear illumination light can be output from the light guide member52in the main scanning direction. Moreover, even when the near end of the exit surface56is disposed near the entrance surface54, the uniformity of the illumination light output from the exit surface56is maintained. Thus, the light guide member52can be configured in a minimal length. Moreover, even when the light guide member52is formed from a member obtained by metal-molding a translucent resin material, the mold shape will not be complex since it will suffice by providing protrusions of a semi-oval body to the mold. In addition, since the light guide member52can be formed in a minimal length, there is another advantage in that the light guide member will not warp easily.

The preferred embodiments of the present disclosure were explained above, the present disclosure is not limited thereto and, for example, may also adopt the following modified embodiments.

(1) In the foregoing embodiment, illustrated was the reflection pattern surface58P configured by juxtaposing the plurality of concave part arrays58L of the oval concave part58in a predetermined pitch in the main scanning direction. However, so as long as the oval concave part58has the foregoing ratio of long diameter d:depth h and the long diameter thereof is oriented in the sub scanning direction, there is no particular limitation in the way of arrangement of the number of oval concave parts58to be arranged. Note that the long diameter direction of the oval concave part58and the sub scanning direction do not need to be completely consistent, and there may be a slight offset between the two.

For example, the reflection pattern surface58P may also be configured by arranging the oval concave part58in the sub scanning direction, not linearly but in a zigzag, and juxtaposing a plurality of such zigzag arrays in the main scanning direction. Moreover, each oval concave part58does not have to be completely independent and, for example, in a case where a plurality of oval concave parts58are arranged in the sub scanning direction, the adjacent oval concave parts58may be united near the edge in the long diameter direction. Moreover, all oval concave parts58do not need to be formed in the same size, and the reflection pattern surface58P may be configured such that the oval concave parts58of different sizes coexist.

(2) In the foregoing embodiment, illustrated was an example of providing, on the reflecting surface57of the light guide member52, only the reflection pattern surface58P formed from the oval concave part58. It will suffice if the reflection pattern surface58P of the oval concave parts58is disposed at least in a region near the entrance surface54of the main body part53which mainly generates the direct light DL, and the other portions of the reflecting surface57may be another reflection pattern surface formed from a plurality of reflective concave parts that do not include a deflection surface.

FIG. 12is a perspective view showing the light guide member52A according to a modified embodiment. With the light guide member52A, the reflection pattern surface formed on the reflecting surface57is formed from patterns which are different in a first region R1near the entrance surface54of the main body part53, and a second region R2on a far end side that is farther than the first region R1. In the first region R1is formed a first reflection pattern surface58P1including the foregoing oval concave parts58. Meanwhile, in the second region R2is formed a second reflection pattern surface58P2including a pattern formed from a plurality of arrays of a V-shaped prism configured from a V-shaped concave groove extending in the sub scanning direction and which does not possess the function of deflecting the illumination light.

As previous explained with reference toFIG. 4, the direct light DL is mainly generated in the first region R1near the entrance surface54. Meanwhile, since the indirect light IL will be dominant in the second region R2, the necessity to diffuse the illumination light is low. Accordingly, it is possible to substantially ensure the uniformity of the linear illumination light that is output from the light guide member52even with a way where the oval concave parts58, which are reflective concave parts including a deflection surface, are arranged only in the first region R1.

(3) In the foregoing embodiment, illustrated was the oval concave part58configured from a semi-oval body as the reflective concave part including a deflection surface. It will suffice if the reflective concave part includes a deflection surface which deflects, in the sub scanning direction, the illumination light in a direction in which the reflection angle widens, and then reflects the illumination light, and is not limited to an oval curved surface. For example, the deflection surface may also be formed as an aspheric surface.

(4) In the foregoing embodiment, illustrated was an example of using a phosphor excitation-type white LED51L as the light source51. Alternatively, it is also possible to use a white LED which creates a white light by combining three LEDs that respectively emit the light's three primary colors. Moreover, a point light source other than an LED may also be used.

As described above, according to the present disclosure, it is possible to output a uniform illumination light using a light guide member of a minimal size. Accordingly, the light guide member can be miniaturized, and the illuminating device comprising this light guide member, and the image reading apparatus and the image forming apparatus using this illuminating device can also be miniaturized.