JP6314871B2 - Light guide, illumination device, and image reading device - Google Patents

Description

  The present invention relates to a light guide, an illuminating device, and an image reading device, and more particularly to a technique for reflecting light incident on a light guide toward an exit surface.

  In an image forming apparatus such as a multifunction machine, as a light source unit of an image reading apparatus such as a scanner, a rod-shaped resin light guide and an LED that emits light from the side in the length direction of the light guide to the inside of the light guide Some use a line light source that combines the above. The light source unit needs to illuminate the document to be read in a line in accordance with the reading of the line sensor. For this purpose, a light reflection or light scattering pattern is provided on the reflection surface opposite to the emission surface for emitting light from the light guide, and the light incident on the light guide is deflected toward the emission surface by the pattern. The linear illumination light is emitted in the direction toward the document.

  Here, in the combination of the rod-shaped light guide and the LED, the direct light deflected directly from the LED on the light reflection or diffusion pattern surface and the light reflection or diffusion pattern surface after being totally reflected on the outer periphery of the light guide at least once. The illumination intensity is different from that of the indirect light deflected by. At positions close to the LED incident surface in the main scanning direction, the illumination light emitted from the respective positions in the length direction of the light guide and the emission surface cannot be obtained. Therefore, as shown in Patent Document 1, by making the cross-sectional shape of the light guide from a circular shape to a polygonal shape and an irregular shape in the main scanning direction, direct light from the LED is not incident on the light reflection or diffusion pattern surface. Lighting units have been proposed.

  Also, as shown in Patent Document 2 below, an illumination unit has also been proposed in which two types of prisms having different shapes are arranged on a reflection surface so that the illuminance distribution of direct light and indirect light is made uniform.

Japanese Patent Laid-Open No. 10-241432 JP2013-157841A

  However, in the illumination system using only indirect light as shown in Patent Document 1, it is necessary to totally reflect the incident light at the outer periphery of the light guide at least once, so that the illumination light obtained in the vicinity of the LED incident surface is There will be almost nothing. For this reason, in order to obtain the necessary illumination light, a distance from the vicinity of the LED incident surface is necessary, and it becomes necessary to lengthen the light guide relative to the size of the document to be read, which hinders downsizing of the apparatus. Become.

  In addition, when two types of prisms having different shapes are employed as shown in Patent Document 2, accuracy is required for forming each shape, and precision tools for processing the two types of prisms are required. Incurs cost increase. Furthermore, when the two types of prism shapes are not accurate and formed differently from the design value, the assumed amount of reflected light cannot be obtained, resulting in illumination unevenness in the main scanning direction.

  The present invention has been made to solve the above-described problem, and ensures the uniformity of the angular distribution of illumination light in the sub-scanning direction at each position in the main scanning direction with the minimum necessary size in the main scanning direction. With the goal.

A light guide according to one aspect of the present invention is a light guide that includes a light transmitting member extending in an optical axis direction of light incident therein, and reflects incident light in a certain direction.
An incident surface provided on at least one of both ends in the longitudinal direction, on which light emitted from the light source is incident;
Forming a part of the outer peripheral surface extending in the optical axis direction of the light incident from the incident surface, and an exit surface for emitting the incident light;
Extending in the optical axis direction at a position opposed to the emission surface, and a anti-reflecting surface that reflects toward the light the incident on the exit surface,
Two types of light reflection patterns, a first light reflection pattern and a second light reflection pattern having different shapes, are formed on the reflection surface,
The first light reflecting pattern includes a reverse V-shaped prism extending along the optical axis direction and an inverted V-shaped prism extending along a direction orthogonal to the optical axis direction in a lattice shape. A light reflection pattern formed in a region from the incident surface to a predetermined distance in the optical axis direction,
The second light reflection pattern is a light reflection pattern in which inverted V-shaped prisms extending along a direction orthogonal to the optical axis direction are provided at regular intervals in the optical axis direction. Formed in a region away from the predetermined distance in the optical axis direction from the surface,
The outer peripheral surface portion other than the entrance surface, the exit surface and the reflection surface, from the entrance surface to the boundary between the first light reflection pattern and the second light reflection pattern in the optical axis direction It is a light guide in which a deflection shape for deflecting the incident light toward the reflection surface is formed in a region.

  According to the present invention, it is possible to ensure the uniformity of the angular distribution of illumination light in the sub-scanning direction at each position in the main scanning direction with the minimum necessary size in the main scanning direction.

1 is a front cross-sectional view illustrating a structure of an image forming apparatus having an illuminating device according to Embodiment 1 of the present invention in an image reading apparatus. 1 is an internal side view showing a schematic configuration of an image reading apparatus according to Embodiment 1 of the present invention. It is the perspective view which shows the illuminating device which concerns on Embodiment 1 of this invention, and is the figure which showed the internal structure. It is a perspective view which shows the light reflection pattern formed in the reflective surface inside the light guide which concerns on Embodiment 1 of this invention. It is a perspective view which expands and shows the light reflection pattern formed in the reflective surface which concerns on Embodiment 1 of this invention. It is a figure which shows the spreading | diffusion distribution of the reflected light in the subscanning direction by the light reflection pattern which concerns on Embodiment 1 of this invention with a graph. It is a side view which shows the state which visually recognized the light guide which concerns on Embodiment 1 of this invention from the entrance plane side. It is a side view which shows the state which visually recognized another example of the light guide which concerns on Embodiment 1 of this invention from the entrance plane side. It is a perspective view which shows the internal structure of the illuminating device which concerns on Embodiment 2 of this invention. It is a figure which shows the light distribution characteristic in each position of the main scanning direction of the light guide concerning the comparative example 1. FIG. (A) is a figure which shows the light distribution characteristic in each position of the main scanning direction of the light guide concerning the comparative example 2, (B) is each position of the main scanning direction of the light guide concerning Embodiment 2. It is a figure which shows the light distribution characteristic in. It is a side view which shows the state which visually recognized an example of the light guide concerning the modification 1 from the entrance plane side. It is a side view which shows the state which visually recognized an example of the light guide concerning the modification 1 from the entrance plane side. It is a side view which shows the state which visually recognized an example of the light guide concerning the modification 1 from the entrance plane side. It is a side view which shows the state which visually recognized the light guide concerning the modification 2 from the entrance plane side.

  Hereinafter, a light guide according to an embodiment of the present invention and a lighting device including the light guide will be described with reference to the drawings.

<Embodiment 1>
FIG. 1 is a front cross-sectional view showing the structure of an image forming apparatus having an illuminating apparatus according to Embodiment 1 of the present invention in an image reading apparatus.

  The image forming apparatus 1 according to the first exemplary embodiment of the present invention is a multifunction machine having a plurality of functions such as a copy function, a printer function, a scanner function, and a facsimile function. The image forming apparatus 1 includes an apparatus main body 11A including an operation unit 47, an image forming unit 12A, a fixing unit 13, a paper feeding unit 14, a document feeding unit 6, an image reading device 5, and the like.

  The operation unit 47 receives instructions such as an image forming operation execution instruction and a document reading operation execution instruction from the operator regarding various operations and processes that can be executed by the image forming apparatus 1. The operation unit 47 includes a display unit 473 that displays operation guidance to the operator.

  When the image forming apparatus 1 performs an original reading operation, the image reading apparatus 5 optically processes an original fed by the original feeding unit 6 or an image of an original placed on contact glass (original placing glass) 161. Read and generate image data. Image data generated by the image reading device 5 is stored in a built-in HDD or a computer connected to a network.

  When the image forming apparatus 1 performs an image forming operation, the image data generated by the document reading operation, the image data received from a user terminal device such as a computer or a smartphone connected to a network, or stored in a built-in HDD. Based on the image data and the like, the image forming unit 12A forms a toner image on the recording paper P as a recording medium fed from the paper feeding unit. The image forming units 12M, 12C, 12Y, and 12Bk of the image forming unit 12A include a photosensitive drum, a developing device that supplies toner to the photosensitive drum, a toner cartridge (not shown) that stores toner, and a charging device. And an exposure device and a primary transfer roller 126, respectively.

  When performing color printing, the magenta image forming unit 12M, the cyan image forming unit 12C, the yellow image forming unit 12Y, and the black image forming unit 12Bk of the image forming unit 12A each store image data. A toner image is formed on the photosensitive drum 121 by charging, exposure, and development processes based on the image composed of each color component, and the toner image is driven by the primary transfer roller 126 by the driving roller 125a and the driven roller 125b. The image is transferred onto the intermediate transfer belt 125 that is stretched around the belt.

  The intermediate transfer belt 125 is driven by a driving roller 125 a in a state where an image carrying surface on which a toner image is transferred is set on the outer peripheral surface thereof and in contact with the peripheral surface of the photosensitive drum 121. The intermediate transfer belt 125 travels endlessly between the driving roller 125a and the driven roller 125b while being synchronized with each photosensitive drum 121.

  The toner images of the respective colors transferred onto the intermediate transfer belt 125 are superimposed on the intermediate transfer belt 125 with the transfer timing adjusted to become a color toner image. The secondary transfer roller 210 conveys the color toner image formed on the surface of the intermediate transfer belt 125 from the sheet feeding unit 14 through the conveyance path 190 at the nip N between the intermediate transfer belt 125 and the driving roller 125a. The recording sheet P is transferred. Thereafter, the fixing unit 13 fixes the toner image on the recording paper P to the recording paper P by thermocompression bonding. The recording paper P on which the color image has been formed after completion of the fixing process is discharged to a discharge tray 151.

  The paper feed unit 14 includes a plurality of paper feed cassettes. The control unit (not shown) rotates the pickup roller 145 of the paper feed cassette in which the recording paper of the size specified by the instruction from the operator is rotated, so that the recording paper P stored in each paper feed cassette is loaded. It is conveyed toward the nip portion N.

  Next, the configuration of the image reading apparatus will be described. FIG. 2 is an internal side view showing a schematic configuration of the image reading device 5.

  As shown in FIG. 2, the image reading device 5 includes an optical scanning device 7 and an imaging unit 8.

  The optical scanning device 7 includes a first optical system unit 71 and a second optical system unit 72.

  The first optical system unit 71 includes the illumination device 10 and a first mirror 711. The illuminating device 10 is disposed below and facing the contact glass 161 so as to irradiate the reading surface of the original, that is, upward. The illuminating device 10 includes a rod-shaped light guide and a light source disposed at an end portion in the length direction of the light guide (details will be described later). The illuminating device 10 extends in the depth direction in FIG. 2, and the extending direction of the illuminating device 10 is the main scanning direction during document reading.

  The first mirror 711 receives the reflected light from the original reading surface of the light irradiated by the illuminating device 10 on the original placed on the contact glass 161 and changes the direction in the horizontal direction. The first mirror 711 is disposed below the contact glass 161. The illumination device 10 and the first mirror 711 are attached to a support member (not shown).

  The second optical system unit 72 includes a second mirror 721 and a third mirror 722. The second mirror 721 receives the light reflected by the first mirror 711 of the first optical system unit 71 and further changes the direction downward substantially vertically. The third mirror 722 further changes the direction of the light reflected by the second mirror 721 substantially horizontally and guides the light toward the imaging unit 8. The second mirror 721 and the third mirror 722 are attached to a support member (not shown).

  The illumination device 10 and each of the mirrors provided in the first optical system unit 71 and the second optical system unit 72 have an elongated shape extending in the main scanning direction with substantially the same length as the contact glass 161.

  Inside the image reading device 5, an unillustrated moving rail for guiding the movement of the optical scanning device 7 in the direction of the arrow is provided. As a result, the optical scanning device 7 including the first optical system unit 71 and the second optical system unit 72 is parallel to the surface of the contact glass 161 so as to read image information on the entire reading surface of the document placed on the contact glass 161. In addition, it is possible to reciprocate in the sub-scanning direction (direction orthogonal to the main scanning direction), that is, the arrow direction shown in FIG.

  The imaging unit 8 is fixed to the inside lower part of the image reading device 5. The imaging unit 8 includes an imaging lens 81 that is an optical member, and a line sensor 82 that is an imaging element. Reflected light from the reading surface of the document reflected by the third mirror 722 of the second optical system unit 72 is incident on the imaging lens 81. The imaging lens 81 forms an image of the reflected light on the surface of the line sensor 82 provided on the downstream side of the optical path. The line sensor 82 generates a voltage indicating the amount of light according to the amount of light received, that is, converts the optical information obtained by the line sensor 82 as a light receiving element into an electrical signal and outputs it to a control unit (not shown). . In this manner, the line sensor 82 reads an image of a document to be read by the image reading device 5.

  Next, the illumination device 10 provided in the image reading device 5 will be described. FIG. 3 is a perspective view showing the lighting apparatus 10 and shows the internal configuration.

  The illumination device 10 includes a light guide 11 and a light source 12.

  The light guide 11 extends in the optical axis direction of light incident from the light source 12 into the light guide 11. Since the light guide 11 extends in the main scanning direction as described above, the optical axis direction coincides with the main scanning direction. The light guide 11 is made of, for example, a resin light transmissive member, and reflects light incident from the light source 12 toward a certain direction (a direction toward the emission surface 17) by the reflection surface 15.

  The light guide 11 is formed by an incident surface 18, an exit surface 17, a reflective surface 15, and a side surface portion 19.

  The incident surface 18 has at least one side surface of both end portions in the longitudinal direction of the light guide 11 as the incident surface. In the present embodiment, a mode in which only one side surface of both end portions is the incident surface 18 will be described. A light source 12 is attached to the incident surface 18. Light emitted from the light source 12 enters the light guide 11 from the incident surface 18.

  The emission surface 17 extends in the main scanning direction and forms one side surface of the light guide 11. In the present embodiment, the emission surface 17 forms the upper surface portion of the light guide 11. Light that has entered the light guide 11 from the incident surface 18 is reflected by the reflecting surface 15 and is emitted from the light emitting surface 17 to the outside of the light guide 11.

  The reflection surface 15 extends in the main scanning direction at a position facing the emission surface 17. In the present embodiment, the reflecting surface 15 forms the lower surface portion of the light guide 11. A plurality of light reflection patterns 16 that reflect incident light toward the emission surface 17 are formed on the reflection surface 15. The reflection surface 15 reflects the light incident on the inside of the light guide 11 from the incident surface 18 toward the emission surface 17 by the light reflection pattern 16. The light reflection pattern 16 is integrally formed of the same material as the light guide 11.

  The side surface portion 19 is an outer peripheral surface portion of the light guide 11 other than the entrance surface 18, the exit surface 17, and the reflection surface 15. When the light guide 11 is viewed with the reflective surface 15 as the lower side, the light guide 11 corresponds to the side portion.

  The light source 12 includes, for example, an LED 1210. The light source 12 is attached to the outer surface of the incident surface 18 of the light guide 11. In the present embodiment, an example in which six LEDs 1210 are provided as the light source 12 is shown. The irradiation direction (optical axis direction) of light that the light source 12 irradiates from the incident surface 18 toward the inside of the light guide 11 is the length direction of the light guide 11, that is, the main scanning direction.

  Next, the light reflection pattern 16 will be described. FIG. 4 is a perspective view showing the light reflection pattern 16 formed on the reflection surface 15 inside the light guide 11.

  The light reflection pattern 16 is a shape pattern that reflects and scatters light incident on itself. On the reflection surface 15, a plurality of light reflection patterns 16 are arranged in a row in the sub-scanning direction, and a plurality of rows made of the plurality of light reflection patterns 16 are arranged in the main scanning direction. The row of the light reflection patterns 16 is formed in the main scanning direction from the position of the incident surface 18 of the reflecting surface 15 to the position of the side surface that is the end opposite to the incident surface 18.

  When the light incident on the light guide 11 from the incident surface 18 has no light reflection or scattering pattern, the light is incident on the light guide 11 and then totally reflected on the outer peripheral surface of the light guide 11. The light travels in the main scanning direction and is guided to the end opposite to the incident surface 18. In this case, since the illumination of the original with light from the light source 12 installed on the incident surface 18 is insufficient, the light reflecting pattern 16 is formed on the reflecting surface 15 facing the light emitting surface 17 to thereby form the light emitting surface 17. The incident light is reflected in the direction and the sub-scanning direction.

  Here, the diffusion in the sub-scanning direction when light incident from the incident surface of a general light guide is reflected by the reflecting surface and emitted from the emitting surface will be described. FIG. 5 is a view showing the light guide 11 having a light reflection pattern. FIG. 6 is a graph showing the diffusion distribution of reflected light in the sub-scanning direction by the light reflection pattern.

  As shown in FIG. 5, a light guide 11 is generally known in which a light reflection pattern 16 formed of an inverted V-shaped prism protruding toward an emission surface 17 is formed on a reflection pattern surface 1601. . The light reflection pattern 16 is integrally formed of the same material as the light guide 11. In such a light guide 11, the reflection pattern surface 1601 of the light reflection pattern 16 is changed to the emission surface 17 by changing the pitch in the main scanning direction between the light reflection patterns 16, the height and width of the light reflection pattern 16, and the like. The amount of light reflected in the direction can be adjusted. For this reason, it is possible to make the illumination light emitted from each position in the main scanning direction uniform by adjusting the pitch, height, width, etc. of the light reflecting pattern 16 arranged at each position in the main scanning direction. It is.

  However, the light source 12 having an LED emits light in the entire circumferential direction of the light guide 11. For this reason, direct light directly incident on the reflective pattern surface 1601 from the light source 12 and indirect light incident on the reflective pattern surface 1601 after being totally reflected from the light source 12 on the outer peripheral surface of the light guide 11 at least once are generated. . These direct light and indirect light have different light beam angles in the sub-scanning direction incident on the reflective pattern surface 1601. Since direct light is light directly incident on the reflective pattern surface 1601 from the LED, the angle with respect to the reflective pattern surface 1601 is shallow, and the light angle distribution in the sub-scanning direction emitted from the emission surface 17 becomes narrow. On the other hand, indirect light is light that enters the reflection pattern surface 1601 from the entire circumferential direction of the outer circumferential surface of the light guide 11 by total reflection. The reflection pattern surface 1601 made of the above inverted V-shaped prism reflects and emits light at the same angle as the incident light beam angle with respect to the sub-scanning direction, and has no deflection component. For this reason, the light beam angle distribution in the sub-scanning direction after emission differs between direct light and indirect light as shown in FIG. 6 according to the incident angle of the direct light and indirect light with respect to the reflection pattern surface 1601.

  Here, in the light guide 11, the ratios of direct light and indirect light are different at each position in the main scanning direction. In particular, in the vicinity of the incident surface 18 in the light guide 11, the proportion of indirect light is significantly smaller than the proportion of direct light. For this reason, the illumination distribution in the sub-scanning direction is greatly different between the vicinity of the incident surface 18 in the light guide 11 and the position away from the incident surface 18 in the light guide 11. That is, the light emitted from the light guide 11 has a different illumination distribution in the sub-scanning direction at each position in the main scanning direction.

  For this reason, if the document reading position is shifted due to the reading operation or the document is lifted off the surface of the contact glass 161, the reading position is shifted in the sub-scanning direction. The deviation from the reference data is not uniform throughout the main scanning direction, and there is a possibility that uneven reading density occurs in the main scanning direction of the image when the original is read.

  The light guide 11 according to the present embodiment has the following shape of the side surface portion 19 of the light guide 11 in order to ensure the uniformity of the angular distribution of illumination light in the sub-scanning direction at each position in the main scanning direction. The shape shown in FIG.

  FIG. 7 is a side view showing a state where the light guide 11 is viewed from the incident surface 18 side. As shown in this figure, the region 192 near the incident surface 18 in the side surface portion 19 of the light guide 11, that is, the region 192 located within a predetermined distance A from the incident surface 18 in the optical axis direction, A deflection shape including a plurality of groove portions 1921 is formed. Each groove portion 1921 has a V-shaped groove shape extending in a direction orthogonal to the optical axis direction.

  A part of the light incident on the light guide 11 from the incident surface 18 is reflected and diffused by the groove portion 1921 formed in the side surface portion 19. A part of the light diffused in the groove 1921 travels toward the reflecting surface 15. As described above, the groove portion 1921 formed in the side surface portion 19 diffuses the light incident from the incident surface 18, thereby deflecting part of the light toward the reflecting surface 15. The ratio of indirect light can be increased by forming the groove portion 1921 in 19. In the light guide 11, since the groove portion 1921 is formed in a region 192 in the vicinity of the incident surface 18 in which the proportion of indirect light is significantly less than the proportion of direct light, the vicinity of the incident surface 18 in the light guide 11. The ratio of indirect light at can be close to the ratio of indirect light at other positions. For this reason, the light distribution by the light guide 11 at each position in the main scanning direction can be made uniform to prevent illumination unevenness.

  In addition, as shown in FIG. 8, the shape of each groove part 1921 is good also as a groove shape extended in the direction parallel to an optical axis direction instead of the groove shape extended in the direction orthogonal to an optical axis direction. Even in this case, the groove portion 1921 can play a role of deflecting light incident from the incident surface 18 toward the reflecting surface 15.

  The light guide 11 is generally manufactured by mold processing. However, when the shape of each groove portion 1921 is a groove shape extending in a direction parallel to the optical axis direction as described above, a so-called undercut process is required. For this reason, it is necessary to manufacture a complicated mold, and the mold cost increases. In this regard, when the shape of each groove portion 1921 is a groove shape extending in a direction orthogonal to the optical axis direction, an undercut process is unnecessary. For this reason, a metal mold | die process becomes easy and the manufacturing cost of the light guide 11 can be held down.

<Embodiment 2>
In the light guide 11 according to the first embodiment, the light reflection patterns 16 having the same shape are arranged in parallel at the same interval on the reflection surface 15. That is, in the light guide 11 according to the first embodiment, the type of the light reflection pattern 16 formed on the reflection surface 15 is one. On the other hand, in the light guide 11 according to the second embodiment, a plurality of types of light reflection patterns having different shapes and / or installation intervals are formed on the reflection surface 15.

  FIG. 9 is a perspective view illustrating an internal configuration of the lighting apparatus 10 according to the second embodiment. In the example shown in this figure, two types of light reflection patterns, a first light reflection pattern 16B and a second light reflection pattern 16C, are formed on the reflection surface 15.

  In the first light reflection pattern 16B, an inverted V-shaped prism 162 extending along the sub-scanning direction and an inverted V-shaped prism 163 extending along the main scanning direction are provided in a staggered pattern (lattice pattern). Light reflection pattern. The first light reflecting pattern 16B is formed in a region near the incident surface 18 on the reflecting surface 15 of the light guide 11, that is, a region located within a predetermined distance B from the incident surface 18 in the optical axis direction. ing.

  The second light reflection pattern 16C is the same light reflection pattern as the light reflection pattern 16 formed on the light guide body 11 according to the first embodiment, and an inverted V-shaped prism extending along the sub-scanning direction. It is provided at regular intervals in the main scanning direction. The second light reflection pattern 16 </ b> C is formed in a region away from a predetermined distance B in the optical axis direction from the incident surface 18.

  Since the second light reflection pattern 16C is an inverted V-shaped prism extending along the sub-scanning direction, the light is reflected and emitted at the same angle as the incident light beam angle with respect to the sub-scanning direction. For this reason, the light reflected by the second light reflection pattern 16C is not deflected in the sub-scanning direction. On the other hand, the first light reflection pattern 16B is a light reflection pattern in which V-shaped prisms are provided in a staggered pattern in the sub-scanning direction and the main scanning direction. For this reason, the light reflected by the first light reflection pattern 16B is deflected in the sub-scanning direction.

  In the light guide 11 according to the second embodiment, the first light reflection pattern 16B is formed in a region near the incident surface 18 on the reflection surface 15, and thus the light distribution by the light guide 11 at each position in the main scanning direction. Unevenness can be suppressed.

  In addition, in the light guide 11 according to the second embodiment, in addition to the two types of light reflection patterns of the first light reflection pattern 16B and the second light reflection pattern 16C being formed on the reflection surface 15, the embodiment is implemented. Similarly to the light guide 11 according to the first embodiment, the side surface 19 of the light guide 11 is formed with a deflection shape including a plurality of grooves 1921. Specifically, a deflection shape including a plurality of groove portions 1921 is formed on the side surface portion 19 located between the boundary position D of the first light reflection pattern 16B and the second light reflection pattern 16C and the incident surface 18. Yes. As a result, it is possible to suppress unevenness in light distribution that could not be eliminated simply by forming the two types of light reflection patterns of the first light reflection pattern 16B and the second light reflection pattern 16C on the reflection surface 15. .

  Here, the light distribution of the light reflected by the first light reflection pattern 16B is different from the light distribution of the light reflected by the second light reflection pattern 16C. For this reason, in the peripheral region of the boundary position D between the first light reflection pattern 16B and the second light reflection pattern 16C, uneven light distribution due to the difference in the light distribution of the light occurs. In this respect, a deflection shape including a plurality of groove portions 1921 is formed on the side surface portion 19 located between the boundary position D of the first light reflection pattern 16B and the second light reflection pattern 16C and the incident surface 18. Therefore, it is possible to suppress the light distribution unevenness.

  The inventors measured light distribution characteristics at each position in the main scanning direction for the light guide according to Comparative Example 1 and the light guide according to Comparative Example 2 in addition to the light guide 11 according to the second embodiment. .

  Similar to the light guide 11 according to the second embodiment, the light guide according to the first comparative example has two types of light reflection patterns, the first light reflection pattern 16B and the second light reflection pattern 16C, on the reflection surface 15. Although the light guide is formed, the side surface 18 of the light guide is not formed with a deflection shape including a plurality of grooves 1921. Similar to the light guide 11 according to the second embodiment, the light guide according to the second comparative example has two types of light reflection patterns, the first light reflection pattern 16B and the second light reflection pattern 16C, on the reflection surface 15. The deflection shape formed of the plurality of groove portions 1921 is formed on the side surface portion 19, but the region where the deflection shape is formed is the boundary between the first light reflection pattern 16B and the second light reflection pattern 16C. The light guide is a region farther from the incident surface 18 than the position D.

  FIG. 10 is a diagram illustrating light distribution characteristics at each position in the main scanning direction of the light guide according to the first comparative example. FIG. 11A is a diagram illustrating light distribution characteristics at each position in the main scanning direction of the light guide according to Comparative Example 2. FIG. 11B is a diagram illustrating light distribution characteristics at each position in the main scanning direction of the light guide 11 according to the second embodiment. In each figure, the position of the incident surface 18 is the main scanning position 0 mm.

  Referring to FIG. 10, in the light guide according to Comparative Example 1, in the peripheral region (main scanning positions 45 mm to 55 mm) of the boundary position D between the first light reflection pattern 16B and the second light reflection pattern 16C, Light distribution unevenness occurs because the light distribution reflected by the first light reflection pattern 16B is different from the light distribution reflected by the second light reflection pattern 16C.

  Next, referring to FIG. 11A, even when the side surface 19 is formed with a deflection shape including a plurality of grooves 1921, the region where the deflection shape is formed is the first light reflection. When the region is farther from the incident surface 18 than the boundary position D between the pattern 16B and the second light reflection pattern 16C, it can be seen that the uneven light distribution seen in FIG. 10 cannot be eliminated.

  On the other hand, referring to FIG. 11B, a plurality of groove portions 1921 are formed on the side surface portion 19 located between the boundary position D of the first light reflection pattern 16B and the second light reflection pattern 16C and the incident surface 18. It is understood that the light distribution unevenness seen in FIG. 10 can be eliminated by forming the deflection shape as described above, and the light distribution by the light guide 11 at each position in the main scanning direction can be made uniform to prevent the generation of illumination unevenness. This is because light is reflected in a deflected shape composed of a plurality of groove portions 1921 of the side surface portion 19, thereby distributing the light reflected by the first light reflecting pattern 16 </ b> B and the light reflected by the second light reflecting pattern 16 </ b> C. This is probably because the difference from the light distribution has been relaxed.

  The present invention is not limited to the configuration of the above embodiment, and various modifications can be made. You may partially combine the structure shown in said embodiment and the following modification.

<Modification 1>
FIG. 12 is a side view showing a state in which an example of the light guide 11 according to Modification 1 is viewed from the incident surface 18 side. As shown in the figure, the deflection shape formed on the side surface portion 19 may include a plurality of recesses 1922 formed as a recess shape toward the inner side of the light guide 11.

  FIG. 13 is a side view showing a state in which another example of the light guide 11 according to Modification 1 is viewed from the incident surface 18 side. As shown in the figure, the deflection shape formed on the side surface portion 19 may include a plurality of convex portions 1923 formed as a convex shape toward the outer side of the light guide 11.

  FIG. 14 is a side view showing a state in which another example of the light guide 11 according to Modification 1 is viewed from the incident surface 18 side. As shown in the figure, the deflection shape formed on the side surface portion 19 may be a textured shape formed by silk printing (see enlarged view). Thereby, a deflection shape can be formed on the side surface portion 19 of the light guide 11 by a simple manufacturing process.

  A part of the light that has entered the light guide 11 from the incident surface 18 is reflected and diffused by the deflection shape formed on the side surface portion 19. Part of the diffused light travels toward the reflecting surface 15. As described above, the deflecting shape plays a role of diffusing the light incident from the incident surface 18 to deflect a part of the light toward the reflecting surface 15. The same effect as in the second mode is obtained. That is, it is possible to suppress uneven light distribution that occurs in a region in the vicinity of the incident surface 18 and a peripheral region of the boundary position D between the first light reflection pattern 16B and the second light reflection pattern 16C.

<Modification 2>
FIG. 15 is a side view showing a state in which the light guide 11 according to the second modification is viewed from the incident surface 18 side. In the light guide 11 according to the second modification, a deflection member 1924 made of a material different from that of the light transmitting member constituting the light guide 11 is formed in the region 192 of the side surface portion 19 where the deflection shape is formed.

Specifically, a substance having a high light reflectance such as aluminum is attached on the region 192 of the side surface portion 19 by a technique such as vacuum deposition. As a result, the region 192 of the side surface portion 19 is coated with a material having a high light reflectance such as aluminum, and the deflection member 1924 is formed. The deflecting member 1924 plays a role of reflecting light leaking from the side surface portion 19 to the outside of the light guide body 11 without being reflected by the deflection shape formed on the side surface portion 19 to the inside of the light guide body 11. By providing the deflection member 1924 in the region 192 where the deflection shape is formed, the ratio of the light reflected by the deflection shape can be increased, so that the effect of the deflection shape can be further enhanced. That is, it is possible to further suppress uneven light distribution that occurs in a region near the incident surface 18 and a peripheral region of the boundary position D between the first light reflection pattern 16B and the second light reflection pattern 16C .

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 5 Image reader 10 Illuminating device 11 Light guide 12 Light source 16 Light reflection pattern 17 Output surface 18 Incident surface 19 Side surface portion 1921 Groove portion 1922 Concavity portion 1923 Convex portion 1924 Deflection member

Claims (9)

A light guide that consists of a light transmissive member extending in the optical axis direction of light incident on the inside and reflects incident light in a certain direction,
An incident surface provided on at least one of both ends in the longitudinal direction, on which light emitted from the light source is incident;
Forming a part of the outer peripheral surface extending in the optical axis direction of the light incident from the incident surface, and an exit surface for emitting the incident light;
Extending in the optical axis direction at a position opposed to the emission surface, and a anti-reflecting surface that reflects toward the light the incident on the exit surface,
Two types of light reflection patterns, a first light reflection pattern and a second light reflection pattern having different shapes, are formed on the reflection surface,
The first light reflecting pattern includes a reverse V-shaped prism extending along the optical axis direction and an inverted V-shaped prism extending along a direction orthogonal to the optical axis direction in a lattice shape. A light reflection pattern formed in a region from the incident surface to a predetermined distance in the optical axis direction,
The second light reflection pattern is a light reflection pattern in which inverted V-shaped prisms extending along a direction orthogonal to the optical axis direction are provided at regular intervals in the optical axis direction. Formed in a region away from the predetermined distance in the optical axis direction from the surface,
The outer peripheral surface portion other than the entrance surface, the exit surface and the reflection surface, from the entrance surface to the boundary between the first light reflection pattern and the second light reflection pattern in the optical axis direction A light guide in which a deflection shape for deflecting the incident light toward the reflection surface is formed in a region. The light guide according to claim 1, wherein the deflection shape is a groove shape extending in a direction orthogonal to the optical axis direction.   The deflection shape includes a plurality of convex portions formed as convex shapes toward the outer side of the light guide, or a plurality of concave portions formed as concave shapes toward the inner side of the light guide. Or the light guide of Claim 2. The light guide according to claim 1, wherein the deflection shape is a textured shape. The light guide according to claim 4 , wherein the deflection shape is formed by silk printing. In the region of the outer peripheral surface portion of the deflection shape is formed, the deflection member made of a material different from that of the light transmitting member is disposed, guide according to any one of claims 1 to 5 Light body. The light guide according to claim 6 , wherein a material of the deflecting member includes aluminum. The light guide according to any one of claims 1 to 7 ,
A light source that irradiates light in the length direction of the light guide from the incident surface toward the inside of the light guide. A lighting device according to claim 8 ;
An image reading apparatus comprising: a light receiving element that receives reflected light from a document illuminated by light emitted from the light exit surface of the light guide.

Images