JP4929366B2 - Light irradiation apparatus, image reading apparatus and image forming apparatus using the same - Google Patents

Description

  The present invention relates to a light irradiation device including a light guide made of a translucent material that emits light emitted from a light source unit in a specific direction, and an image reading apparatus and an image forming apparatus using the light irradiation device. Is.

  This type of light irradiation apparatus is, for example, in an image reading apparatus that reads an image on a document surface based on reflected light from the document surface received by a light receiving element (Charge Coupled Devices: CCD, Complementary Metal Oxide Semiconductor: CMOS, etc.). It is used as means for irradiating light on the document surface. When a color image is read by an image reading apparatus, generally, reflected light from a document surface is received by individual light receiving elements for each of red (R), green (G), and blue (B). And as shown to Fig.9 (a), each light receiving element corresponding to each color is arrange | positioned so that the position may mutually differ. Therefore, light received by each light receiving element includes reflected light from different points on the document surface. Therefore, the read image indicates that the intensity of light emitted from the light irradiation device is sufficiently large and uniform in the direction on the document surface corresponding to the direction in which the light receiving elements are arranged (left and right in FIG. 9A). It is necessary to improve quality. Specifically, as shown in FIG. 9B, the width of the light receiving surface of each light receiving element (the length in the arrangement direction of each light receiving element) is “a”, and the distance between the centers of the light receiving surfaces of each light receiving element. Is “b” and the reduction ratio of the optical system from the original surface to each light receiving element is “m”, the width on the original surface where the intensity of the irradiated light needs to be increased and made uniform (see FIG. 9 (a) The length in the horizontal direction) X is (a + b × 2 + α) / m. “Α” is a parameter that is appropriately set in consideration of errors such as manufacturing errors.

  For example, the light irradiation device capable of irradiating light with sufficiently high intensity and uniform light in the width X on the document surface is arranged so that the longitudinal direction coincides with the direction orthogonal to the direction of the width X. Some cylindrical xenon lamps are used as the light source section. However, xenon lamps consume a large amount of power and generate a large amount of heat in order to fully meet the recent demands for energy saving and improved reliability of image reading apparatuses. Therefore, a light source unit that consumes less power and generates less heat than a xenon lamp is desired. As such a light source unit, for example, a light emitting diode (LED) can be used. However, LEDs generally have lower light irradiation intensity than xenon lamps. Therefore, when an LED is simply used as a light source unit, it is difficult to irradiate light having a sufficiently large intensity in the width X on the original surface.

  Conventionally, there has been known a light irradiation device in which a light guide made of a translucent material is disposed between a light source unit and a document surface (Patent Document 1). The light irradiation device disclosed in Patent Document 1 includes an LED (light source unit) mounted on a circuit board, and a light guide that guides and emits light incident from the LED toward a document surface. With body. If it is a light irradiation apparatus provided with such a light guide, it becomes possible to collect most of the light irradiated radially from the LED in a narrow area of the width X on the document surface. Therefore, if the light guide is used, even if an LED having a low light irradiation intensity is used as the light source part, it is possible to irradiate the light having a high intensity on the portion having the width X.

  Here, when a light source unit such as an LED that radiates light radially is used, the light is collected in a portion having a width X (irradiation target region) on the document surface, and the irradiation target region is irradiated with light having high intensity. In particular, it is important to emit as much light incident on the incident surface of the light guide as possible from the exit surface of the light guide. And in order to implement | achieve this, it is necessary to suppress that the incident light which injected into the entrance plane of a light guide comes out of a light guide, before reaching an output surface.

FIG. 10 is an explanatory diagram of incident light incident on the light guide. This figure shows the light guide viewed from a direction orthogonal to the width X on the original surface.
Although some incident light that has entered the incident surface 431a of the light guide 431 reaches the exit surface 431b directly through the inside of the light guide, many of them are first connected to connect the entrance surface 431a and the exit surface 431b. The surface 431c is reached. The incident lights L ₁ and L ₂ that have reached the coupling surface 431c pass through the coupling surface 431a according to the incident angles (angles formed with the normal of the coupling surface) θ ₁ and θ ₂ with respect to the coupling surface. If there is, some of the light is reflected by the connecting surface. That is, incident light L ₂ having an incident angle θ ₁ smaller than the critical angle α with respect to the coupling surface 431 c is transmitted through the coupling surface 431 c and exits the light guide, and the incident angle θ ₂ has a critical angle α with respect to the coupling surface 431 c. The incident light L _{1 as} described above is reflected by the connecting surface 431c and finally exits from the exit surface 431b.

For example, the light irradiation device described in FIG. 13 of the above-mentioned patent document can suppress the incident light that has entered the incident surface of the light guide from going out of the light guide before reaching the output surface. Can be mentioned.
In this conventional light irradiation apparatus, as shown in FIG. 11, the incident surface 531a of the light guide 531 is formed in a convex shape so that incident light is incident on the coupling surface 531c as compared with the case where the incident surface is flat. The corners are made larger. Thereby, of the incident light incident from the incident surface 531a, if the incident surface is a flat surface, the incident light with respect to the coupling surface 531c is smaller than the critical angle and transmitted to the outside of the light guide. It is possible to prevent the light from being reflected by the connecting surface 531c and transmitted to the outside of the light guide.
Further, in the conventional light irradiation apparatus, the reflecting member 533 is provided by evaporating aluminum on the outer surface of the connecting surface 531c. As a result, even if the incident surface 531a is formed in a convex shape, incident light whose incident angle with respect to the coupling surface 531c is smaller than the critical angle is reflected by the reflecting member 533 even if it is transmitted outside the light guide. It can return to the inside of a light guide.
As described above, in the conventional light irradiation device, the incident surface 531a of the light guide 531 is formed in a convex shape, and the reflection member 533 is provided on the outer surface of the connecting surface 531c, so that the light is incident from the incident surface 531a. The incident light is prevented from exiting the light guide body before reaching the exit surface.

  However, when the incident surface 531a of the light guide 531 is formed in a convex shape, the manufacturing cost is higher because it is more difficult to manufacture than when the incident surface is formed as a flat surface. In addition, if the reflecting member 533 is provided on the outer surface of the connecting surface 531c, the material cost of the reflecting member 533 is increased, and a step of fixing the reflecting member 533 to the connecting surface outer surface of the light guide 531 is required. Therefore, the manufacturing cost is increased. As described above, in the conventional light irradiation apparatus, incident light incident from the incident surface 531a can be prevented from exiting the light guide body before reaching the exit surface, but the manufacturing cost is high. was there.

  The present invention has been made in view of the above problems, and the object of the present invention is to keep the manufacturing cost low and to make the incident light incident from the incident surface go out of the light guide before reaching the output surface. It is an object of the present invention to provide a light irradiating device that can suppress the occurrence of an image, and an image reading apparatus and an image forming apparatus using the same.

To achieve the above object, the present invention 請 Motomeko 1, the light source comprises a substrate provided on a substrate surface, the exit surface for irradiating light from the light source in a radial, said exit surface substrate Light irradiation comprising: a light source unit facing in a direction along the surface; and a light guide made of a translucent material that guides and emits light incident from the emission surface of the light source unit in a specific direction In the apparatus, the light guide is disposed opposite to the light exit surface of the light source unit and receives an incident plane on which light emitted from the light exit surface of the light source unit is incident, and incident light incident from the incident plane. An exit surface that exits toward the document surface; and a connection surface that connects the entrance plane and the exit surface, and at least a portion of the connection surface that is close to the entrance plane is the entrance plane. If the plane is parallel to the normal direction, the plane is smaller than the critical angle. An inclined portion that is inclined with respect to the normal direction of the incident plane is provided so that a part or all of the incident light that reaches the light source is totally reflected, and the incident plane is the exit surface of the light source unit and the The light guide is arranged so as to face both end faces of the substrate.
The fact, the invention of claim 2, the light irradiation apparatus according to claim 1, in which the center of the entrance plane of the light guide body so as to face the center of the exit surface of the light source unit, disposed light guide body It is characterized by.
According to a third aspect of the present invention, in the light irradiation device according to the first or second aspect , the translucent material constituting the light guide is a resin having light transmissivity.
According to a fourth aspect of the present invention, there is provided an image reading unit comprising: a light irradiating unit that irradiates light on a document surface; and an image reading unit that receives reflected light from the document surface and reads an image on the document surface. In the apparatus, the light irradiation device according to any one of claims 1 to 3 is used as the light irradiation means.
According to a fifth aspect of the present invention, there is provided an image forming apparatus comprising: an image reading unit that reads an image on a document surface; and an image forming unit that forms an image on a recording material based on image information read by the image reading unit. The image reading apparatus according to claim 4 is used as the image reading unit.

Also, in the invention of claim 1, the side close to at least the incident plane of the coupling surface of the light guide, and as a plane parallel to the normal direction of the incident plane of the portion light guide Then, an inclined portion is provided so that a part or all of the incident light that reaches the plane at an angle smaller than the critical angle is totally reflected. That is, in the present invention, when the inclined portion of the coupling surface is a plane parallel to the normal direction of the incident plane of the light guide, the incident light with respect to at least a part thereof is smaller than the critical angle. For the above, the inclined part is oriented so that the incident angle with respect to the inclined part is not less than the critical angle. Thereby, in the light guide which the said inclination part is a plane parallel to the normal line direction of the incident plane of a light guide, the incident light which permeate | transmitted the said inclination part and went out of the light guide is removed. , It can be totally reflected so as not to go out of the light guide. Therefore, it is not necessary to provide a reflecting member on the outer surface of the inclined portion of the connecting surface.

  As described above, according to the present invention, it is possible to prevent incident light from going out of the light guide without providing a reflection member on the outer surface of the connection surface of the light guide, while suppressing manufacturing costs. There is an excellent effect that incident light can be prevented from exiting the light guide before reaching the exit surface.

(A) is explanatory drawing for demonstrating the optical path of the incident light in the specific connection surface of a light guide in the light irradiation apparatus in the scanner part of the copying machine in embodiment. (B) is explanatory drawing for demonstrating the optical path of the incident light in the light guide for a comparison comprised so that the specific connection surface of a light guide may become a plane parallel to the normal line direction of an incident plane. FIG. 2 is a front view schematically showing the internal structure of the copier. Explanatory drawing which shows schematic structure of the light irradiation apparatus when it is a direction orthogonal to the running direction of the 1st traveling body in the scanner part, and it sees from a substantially horizontal direction. The perspective view of the light irradiation apparatus. Explanatory drawing for demonstrating the light distribution of the emitted light of LED in the light irradiation apparatus. Explanatory drawing of the light irradiation apparatus in the modification 1. FIG. Explanatory drawing of the light irradiation apparatus in the modification 2. FIG. The perspective view of the light irradiation apparatus in the modification 3. FIG. (A) And (b) is explanatory drawing for demonstrating the relationship between a document surface and an image formation surface. Explanatory drawing about the incident light which injected into the conventional light guide. Conventional light irradiation device

Hereinafter, an embodiment in which the present invention is applied to a color copying machine as an image forming apparatus will be described. In this embodiment, a color copying machine is taken as an example, but the same applies to a monochrome copying machine.
FIG. 2 is a front view schematically showing the internal structure of a full-color copying machine 1 which is an image forming apparatus to which the present invention is applied. A printer engine 3 for forming a color image is provided at the center of the apparatus main body 2 of the copying machine 1. The printer engine 3 includes four drum-like photoreceptors 4 that are spaced apart at equal intervals and arranged in parallel in the horizontal direction. The printer engine 3 includes four charging rollers 5 that uniformly charge the outer peripheral surface of each photoconductor 4. The printer engine 3 exposes the outer peripheral surface of each photoconductor 4 charged by each charging roller 5 according to the corresponding image data, thereby forming an electrostatic latent image on the outer peripheral surface of each photoconductor 4. An exposure apparatus 6 is provided. In addition, the printer engine 3 supplies toner to the electrostatic latent image on the outer peripheral surface of each photoconductor 4 to visualize each electrostatic latent image as a toner image. The intermediate transfer belt 8 to which the toner images on the photoconductor 4 are sequentially transferred, four cleaning devices 9 for removing the toner remaining on each photoconductor 4 after the transfer of the toner image onto the intermediate transfer belt 8, and the intermediate transfer A transfer roller 10 for transferring the toner image transferred onto the belt 8 onto the recording paper S is provided. Note that toner images of different colors (Y: yellow, M: magenta, C: cyan, K: black) are formed on the four photoconductors 4, and the toner images of these colors are formed on the intermediate transfer belt 8. Are sequentially transferred so as to overlap each other, whereby a color toner image is formed on the intermediate transfer belt 8, and this color toner image is finally formed on the recording paper S.

  In addition, a scanner unit as an image reading unit that reads an image on a document surface is provided on the upper part of the apparatus main body 2. The scanner unit includes an ADF 11 that automatically feeds a document D that is an illumination target to be illuminated by a light irradiation device described later, a contact glass 12 on which the document D is placed, and a document D on the contact glass 12. An image reading mechanism 13 as image reading means for reading an image on the original surface is disposed.

  The image reading mechanism 13 includes a first traveling body 14 and a second traveling body 15 that can travel at a speed of 2: 1 parallel to the contact glass 12, an imaging lens 16, a CCD 17 that is a photoelectric conversion element as a light receiving element, and the like. It is configured. The first traveling body 14 receives a document D placed on the contact glass 12 or a document D conveyed by the ADF 11 and sent onto the contact glass 12 from the bottom of the contact glass 12 onto the document surface. And a first mirror 19 for reflecting the reflected light reflected from the document surface so as to be sent to the CCD 17. A second mirror 20 and a third mirror 21 that further reflect the light reflected by the first mirror 19 are mounted on the second traveling body 15. The light sequentially reflected from the second mirror 20 and the third mirror 21 sequentially from the first mirror 19 enters the CCD 17 through the imaging lens 16 and is received by the CCD 17.

  On the other hand, a plurality of stages, for example, four stages of sheet cassettes 22 for storing recording sheets S as recording materials are provided in the lower part of the apparatus main body 2. The recording sheets S stored in these sheet cassettes 22 are separated and fed one by one by a pickup roller 23 and a feed roller 24. The separated recording paper S is transported along a paper transport path 25 provided in the apparatus main body 2. On the sheet conveyance path 25, a registration roller 26, a transfer roller 10, a fixing device 27, a paper discharge roller 28, and the like are arranged. The registration roller 26 temporarily holds the fed recording sheet S, and the recording sheet S is matched with the timing at which the toner image on the intermediate transfer belt 8 enters the area facing the transfer roller 10 (secondary transfer area). Driving is performed so as to feed the secondary transfer area. Further, the recording paper S on which the toner image is secondarily transferred from the intermediate transfer belt 8 is conveyed to the fixing device 27, and the toner is softened or melted by applying heat and pressure, so that the toner image becomes the recording paper. Fix to S.

Next, an image forming operation in the copying machine 1 will be described.
First, the image reading mechanism 13 reads an image on the document surface of the document D placed on the contact glass 12 or automatically fed by the ADF 11. Then, according to the image information read by the image reading mechanism 13, laser light corresponding to each color is emitted from the four semiconductor lasers of the exposure device 6. Thereby, an electrostatic latent image corresponding to each color is formed on the outer peripheral surface of each photoconductor 4 uniformly charged by the charging roller 5. Each electrostatic latent image is supplied with toner of each color from each developing device 7. As a result, toner images of different colors are formed for the respective photoreceptors 4. The toner images on the respective photoconductors 4 are sequentially primary-transferred so as to overlap each other on the intermediate transfer belt 8 that moves in synchronization with the rotation of the photoconductors 4. As a result, a color toner image is formed on the intermediate transfer belt 8.

  On the other hand, the recording paper S is fed from the paper cassette 22 during the toner image forming operation of the printer engine 3. Then, the recording sheet S is sent to the secondary transfer area at a predetermined timing by the registration roller 26, and the color toner image on the intermediate transfer belt 8 is secondarily transferred onto the recording sheet S. The recording sheet S on which the color toner image is secondarily transferred is continuously conveyed on the sheet conveying path 25 and sent to the fixing device 27. In the fixing device 27, the color toner image on the recording sheet S is fixed on the recording sheet S, and then the recording sheet S is discharged onto a discharge tray 29 by a discharge roller 28.

Next, the configuration of the light irradiation device 18 of the image reading unit, which is a characteristic part of the present invention, will be described.
FIG. 3 is an explanatory diagram showing a schematic configuration of the light irradiation device 18 when viewed from a substantially horizontal direction in a direction orthogonal to the traveling direction of the first traveling body 14.
FIG. 4 is a perspective view of the light irradiation device 18.
As illustrated in FIG. 4, the light irradiation device 18 according to the present embodiment includes a plurality of LEDs 32 that are light source units arranged in a line on an LED array substrate 30 that is a circuit board, and a light guide 31. Yes. The LED array substrate 30 is arranged such that its longitudinal direction is a direction orthogonal to the traveling direction of the first traveling body 14 and extends in a substantially horizontal direction, that is, extends in the main scanning direction of the document D. The The plurality of LEDs 32 are arranged in a line along the longitudinal direction on the LED array substrate 30. On the LED array substrate 30, a wiring pattern (not shown) and various circuit elements for supplying power to each LED 32 are formed. The LEDs 32 in the present embodiment are arranged on the LED array substrate 30 such that the emission surface thereof faces in a direction parallel to the substrate surface of the LED array substrate 30. Therefore, the direction of the center line of light emitted from the emission surface of the LED 32 is substantially parallel to the substrate surface of the LED array substrate 30. In the present embodiment, a case where a plurality of LEDs 32 are arranged in one row will be described as an example, but they may be arranged in a plurality of rows.

  The light guide 31 is made of a light transmissive material such as a transparent resin (acrylic, polycarbonate, etc.) or glass. The light guide 31 is a hexahedral member having a rectangular input plane 31a and an output plane 31b that are longer than the row length of the plurality of LEDs 32. The light guide 31 is disposed between each LED 32 and the document surface. Specifically, the light guide 31 is disposed so that its incident plane 31a is close to or in contact with the output plane of each LED 32, and its output plane 31b faces the document surface. Thus, the light guide 31 receives the light emitted from the LED 32 by the incident plane 31a, guides it toward the document surface, and emits the light from the output plane 31b. In this embodiment, the light guide 31 is attached on the same surface as the substrate surface of the LED array substrate 30 to which the plurality of LEDs 32 are attached. Specifically, one of the two connection surfaces constituting the side surface in the longitudinal direction of the light guide body among the four connection surfaces connecting the incident plane 31a and the emission plane 31b is bonded to the substrate surface of the LED array substrate 30. Or fixed with double-sided tape.

  In the present embodiment, of the four connecting surfaces, the connecting surface fixed to the substrate surface of the LED array substrate 30 is orthogonal to two connecting surfaces that are parallel to each other and constitute the end surface in the longitudinal direction of the light guide. It is configured as follows. In addition, these three connecting surfaces are parallel to the normal line of the incident plane 31a (also the normal line of the output plane). On the other hand, a connection surface (hereinafter referred to as a “specific connection surface”) 31c facing the connection surface fixed to the substrate surface of the LED array substrate 30 is inclined with respect to the normal line of the incident plane 31a. Specifically, the distance between the specific connection surface 31c and the connection surface fixed to the substrate surface of the LED array substrate 30 is formed so as to increase from the incident plane 31a toward the output plane 31b. Therefore, the light guide 31 of the present embodiment has a trapezoidal cut surface when cut along the normal direction of the incident plane 31a so as to pass through the specific connecting surface 31c. The surface corresponding to the side is the incident plane 31a, and the surface corresponding to the trapezoidal long side is the output plane 31b.

  Since the light guide 31 of this embodiment takes a long shape as shown in FIG. 4, as a method of manufacturing the light guide 31 having such a shape, a resin having light transmissivity is used as a mold. It is preferable to adopt a resin mold manufacturing method in which the resin is filled and molded. When manufacturing by this method, since it is necessary to take out molded resin from a metal mold | die, it is desirable to make this shape easy to take out manufacturing cost. The light guide 31 in the present embodiment has a shape that does not narrow from the incident plane 31a toward the exit plane 31b when viewed from any direction orthogonal to the normal direction of the incident plane 31a. . Therefore, when manufacturing the light guide 31, the resin in the mold can be easily taken out from the mold by taking out from the emission plane 31 b side of the light guide 31 when taking out from the mold.

In the present embodiment, as shown in FIG. 3, the LED array substrate 30 is a plate-like member, and light emitted from the emission plane 31 b of the light guide 31 is directed in a direction substantially parallel to the substrate surface. LED32 and the light guide 31 are arrange | positioned so that it may radiate | emit. In the present embodiment, the light emitted from each LED 32 is emitted so as to spread radially from its emission surface, so that the light emitted from the emission plane 31b of the light guide 31 also slightly spreads from the emission plane 31b. Is emitted. Here, when positioning the light guide 31 with respect to the LED array substrate 30, the certainty of the positioning is improved when the entire light guide 31 is disposed on the substrate surface of the LED array substrate 30. However, in this case, when the light guide 31 is attached to the LED array substrate 30 such that the emission plane 31b of the light guide 31 is located on the inner side of the substrate surface than the end surface of the LED array substrate 30 (end surface on the document surface side). A part of the light emitted from the emission plane 31 b of the light guide 31 is blocked by the LED array substrate 30. As a result, there is a problem that the blocked light is not irradiated on the document surface. In particular, in the present embodiment, since the LED 32 having a relatively low light intensity is employed as the light source unit, the spread light emitted from the emission plane 31b of the light guide 31 is preferably transmitted to a specific location on the document surface as much as possible. Specifically, as shown in FIG. 9A, it is desirable to collect in the width X on the document surface. Therefore, it is desirable to arrange so that a part of the light emitted from the emission plane 31 b of the light guide 31 is not blocked by the LED array substrate 30.
Therefore, in the present embodiment, as shown in FIG. 3, the light emission surface 31b of the light guide 31 is placed at the same position as the end surface (end surface on the document surface side) of the LED array substrate 30 or outward (document surface) from the end surface. The light guide 31 is disposed so as to be positioned in a direction close to Thereby, a part of the light emitted from the emission plane 31 b of the light guide 31 is not blocked by the LED array substrate 30. As a result, it is possible to irradiate all the light emitted from the emission plane 31b of the light guide 31 toward the document surface.

  Moreover, in this embodiment, it arrange | positions so that the incident plane 31a of the light guide 31 may adjoin or contact so that the output surface of each LED32 may be opposed, and all the light radiate | emitted from each LED32 is incident on the light guide 31. It is comprised so that it may inject into the plane 31a. When realizing such a configuration, it is desirable to use an LED whose emission surface is flat or concave. This is because, when an LED having a convex emission surface is used, it is necessary to form the light guide 31 so as to cover the convex emission surface, and the manufacturing cost of the light guide 31 increases. Further, when the lead wire of each LED 32 is closer to the light guide 31 than the emission surface of each LED 32, the lead wire interferes so that the incident plane 31 a of the light guide 31 approaches or comes into contact with the emission surface of each LED 32. May not be able to be placed. Therefore, it is desirable to provide the lead wire of each LED 32 at a position farther from the light guide 31 than the emission surface of each LED 32.

FIG. 1A is an explanatory diagram for explaining an optical path of incident light on the specific coupling surface 31 c of the light guide 31. FIG. 1B illustrates an optical path of incident light in the light guide 431 configured such that the specific coupling surface 31c of the light guide 31 is a plane parallel to the normal direction of the incident plane 31a. It is explanatory drawing.
As shown in FIG. 1B, incident light having an angle θ ₂ with respect to the incident plane 431a of the light guide 431 reaches the specific coupling surface 431c with an incident angle θ _{2 with} respect to the specific coupling surface 431c. Since the incident angle θ ₂ is smaller than the critical angle α with respect to the specific coupling surface 431c, the incident light that reaches the specific coupling surface 431c is refracted and transmitted through the specific coupling surface 431c. As a result, this incident light comes out of the light guide 431.

On the other hand, in the light guide 31 of the present embodiment, as shown in FIG. 1A, incident light having an angle θ ₂ with respect to the incident plane 31a of the light guide 31 is relative to the specific coupling surface 31c. Thus, the incident angle θ ₁ reaches the specific coupling surface 31c. In the present embodiment, since the specific coupling surface 31c is inclined at an angle β with respect to the normal N of the incident plane 31a, the incident angle θ ₁ is incident on the light guide 431 shown in FIG. The angle is larger than the angle θ ₂ . More specifically, the incident angle θ ₁ is larger than the critical angle α with respect to the specific coupling surface 31c. For this reason, the incident light that has reached the specific coupling surface 31c is totally reflected by the specific coupling surface 31c. As a result, the incident light travels inside the light guide without exiting the light guide 431, and finally reaches the exit plane 31b of the light guide 31 and is guided from the exit plane 31b. It is emitted outside the body.

Thus, according to the present embodiment, when the specific coupling surface is a plane parallel to the normal direction of the incident plane 431a as shown in FIG. For incident light in which θ ₂ is smaller than the critical angle α, the specific coupling surface is oriented so that the incident angle θ ₁ with respect to the specific coupling surface is equal to or greater than the critical angle α. Thereby, in the light guide 31 in the present embodiment shown in FIG. 1A, the light guide 431 shown in FIG. 1B is transmitted through the specific connection surface 431c and exits to the outside of the light guide. The incident light that has been reflected can be totally reflected so that it does not exit the light guide. Therefore, more incident light can be guided to the emission plane 31b than the light guide 431 shown in FIG. As a result, according to the light irradiation device of the present embodiment, compared with the light irradiation device using the light guide 431 shown in FIG. It is possible to irradiate the portion of width X on the document surface shown in FIG.

  In addition, as shown in FIG.1 (b), when the specific connection surface 431c is a plane parallel to the normal line direction of the incident plane 431a, it is a resin generally used as a light guide material. The incident light that is transmitted through the specific coupling surface 431c when the light is formed is incident on the light guide 431 out of the light emitted from the LED 32 at an angle larger than the half-value angle of the light emitted from the LED 32. The light is incident on the plane 431a.

Here, the meaning of “half-value angle” is as follows.
FIG. 5 is an explanatory diagram showing the light distribution of the emitted light from the LED 32. This light distribution is the light intensity level at each point on the virtual surface that is equidistant from the central point of the output surface on one virtual surface along the normal passing through the center point of the output surface of the LED 32. This is shown as a relative value when the light level at a point located on the normal line is 100. The LED 32 generates a maximum light amount at a point located on the normal line. If the LED 32 has an ideal orientation distribution, the light distribution of the emitted light from the LED 32 is circular, but the LED 32 of this embodiment is elliptical as shown in FIG. An angle γ ₀ between a virtual straight line connecting a point at which the light amount level is 50, that is, half of the maximum light amount, and the center point of the exit surface and a normal passing through the center point of the exit surface is referred to as a half-value angle. The half-value angle γ _{0 of the} light emitted from the LED 32 in this embodiment is approximately 51 ° as shown in FIG.

  In this embodiment, the connection surface 31d facing the specific connection surface 31c, that is, the connection surface 31d fixed to the substrate surface of the LED array substrate 30, is similar to the specific connection surface 431c shown in FIG. It is a plane parallel to the normal direction of the incident plane 31a. For this reason, the connection surface 31d is not different from the light guide 431 shown in FIG. 1B, and the incident light exits from the light guide and cannot be guided to the emission plane 31b. When the incident light is also guided to the emission plane 31b, the substrate surface may be used as a reflection surface by evaporating aluminum on the substrate surface of the LED array substrate 30 to which the coupling surface 31d is fixed. In this case, incident light that has exited the light guide from the connection surface 31d can be reflected by the substrate surface and sent again from the connection surface 31d into the light guide. Thereafter, when this light reaches the specific coupling surface 31c, it is totally reflected by the specific coupling surface 31c and finally guided to the emission plane 31b.

[Modification 1]
Next, a modification of the light irradiation apparatus in the present embodiment (hereinafter, this modification is referred to as “modification 1”) will be described.
FIG. 6 is an explanatory diagram of the light irradiation device 118 according to the first modification.
In the light guide 131 in the first modification, both of the two connection surfaces 131c and 131d constituting the side surface in the longitudinal direction of the light guide among the four connection surfaces connecting the incident plane 131a and the output plane 131b are incident. It is inclined at an angle β with respect to the normal N of the plane 131a. Therefore, the light guide 131 of the first modification has a trapezoidal cut surface when cut along the normal direction of the incident plane 131a so as to pass through these two connecting surfaces 131c and 131d. The surface corresponding to the short side of the trapezoid is the incident plane 131a, and the surface corresponding to the long side of the trapezoid is the output plane 131b.

  Moreover, in this modification 1, as shown in FIG. 6, the LED array substrate 30 is a plate-like member, and the light emitted from the emission plane 131b of the light guide 131 is applied to the substrate surface, as in the above embodiment. On the other hand, the LED 32 and the light guide 131 are arranged so as to emit light in a substantially parallel direction. However, in the first modification, the two connection surfaces 131c and 131d are plane symmetric with respect to a specific surface (a surface parallel to the column direction of the LEDs 32) along the normal direction of the incident plane 131a. Therefore, the LED 32 and the light guide are arranged such that the center of the emission surface 32b of the LED 32 coincides with the center of the incident plane 131a of the light guide 131 in the direction in which both the coupling surfaces 131c and 131d face each other (the left-right direction in FIG. 6). A body 131 is arranged. Thereby, it is possible to prevent the intensity of light emitted from the emission plane 131b of the light guide 131 from being biased in the direction in which both the coupling surfaces 131c and 131d face each other (the left-right direction in FIG. 6).

[Modification 2]
Next, another modified example of the light irradiation apparatus in the present embodiment (hereinafter, this modified example is referred to as “modified example 2”) will be described.
FIG. 7 is an explanatory diagram of the light irradiation device 218 in the second modification.
In the light guide body 231 in the second modification example, only a part of each of the two connection surfaces constituting the side surface in the longitudinal direction of the light guide body among the four connection surfaces connecting the incident plane 231a and the emission plane 231b is incident. It is inclined at an angle β ′ with respect to the normal N of the plane 231a. That is, these two connecting surfaces are respectively the first connecting surface portions 231c and 231d inclined at an angle β ′ with respect to the normal line N of the incident plane 231a, and the second connecting surface parallel to the normal line N. It has surface portions 231e and 231f.

  Incidentally, as the distance from the incident plane 431a increases, the incident angle of the incident light incident from the incident plane 431a with respect to the coupling surface 431c increases. Therefore, even when the connection surface 431c is a plane parallel to the normal direction of the incident plane 431a as in the light guide 431 shown in FIG. 1B, the connection is separated from the incident plane 431a by a predetermined distance or more. At a point on the surface 431c, incident light does not pass through the point on the connecting surface 431c. That is, in the light guide 431 shown in FIG. 1B, the problem that incident light comes out of the light guide occurs only in the portion on the coupling surface 431c close to the incident plane 431a. Therefore, in the second modification, only the portion where this problem occurs is inclined at an angle β ′ with respect to the normal line N of the incident plane 231a to form first connecting surface portions 231c and 231d.

  Here, the boundary between the first connecting surface portions 231c and 231d and the second connecting surface portions 231e and 231f can be determined as follows. That is, when the first connecting surface portions 231c and 231d are parallel to the normal line N of the incident plane 231a and are made one plane, like the second connecting surface portions 231e and 231f, they are incident from the incident plane 231a. Of the incident light, a point at which the incident light whose critical angle is the incident angle with respect to the plane may be set as the boundary.

  The light guide 231 in the second modification is also viewed from any direction orthogonal to the normal direction of the incident plane 231a, similarly to the light guides 31 and 131 in the embodiment and the first modification. In some cases, there is no portion that narrows from the incident plane 231a toward the exit plane 231b. Therefore, when manufacturing the light guide 231, the resin in the mold can be easily taken out from the mold by taking out from the emission plane 231 b side of the light guide 231 when taking out from the mold. Have.

[Modification 3]
Next, still another modification of the light irradiation apparatus in the present embodiment (hereinafter, this modification is referred to as “Modification 3”) will be described.
FIG. 8 is a perspective view of the light irradiation device 318 in the third modification.
The light guide 331 in the third modification has a plurality of protrusions 331e protruding in the vertical direction from the incident plane 331a, and there is a fitting space for fitting each LED 32 between these protrusions 331e. It is formed. Thus, when the light guide 331 is attached to the LED array substrate 30 to which the LEDs 32 are attached, if each LED 32 is fitted into each fitting space of the light guide 331, the LED 32 on the LED array substrate 30 is guided. The relative position with respect to the light body 331 can be easily and accurately positioned.
In addition, in this modification 3, although the fitting space is provided about each of each LED32, there should just be a fitting space in which at least 1 LED32 fits.

As described above, the light irradiation device 218 according to the second modification of the present embodiment includes a plurality of LEDs 32 serving as a light source unit, and a translucent material that guides and emits light emitted from these LEDs 32 in a specific direction. The light guide 231 which consists of is provided. The light guide 231 includes an incident plane 231a on which light from the plurality of LEDs 32 is incident, an output plane 231b that emits incident light incident from the incident plane toward the original surface to be irradiated, and these incident planes. And a connecting surface that connects the output plane. Then, the first connecting surface portion 231c, which is a part of the connecting surface, is inclined with respect to the optical axis of the incident light, and the incident angle of light with respect to the first connecting surface portion 231c is the other portion of the connecting surface. The incident angle increasing portion is made larger than the second connecting surface portion 231e. Thereby, in the light guide 431 shown in FIG. 1B, the incident light that has been transmitted through the connecting surface 431c and has exited the light guide is totally reflected so that it does not exit the light guide. Can be. Therefore, more incident light can be guided to the emission plane 231b than the light guide 431 shown in FIG. As a result, compared with the light irradiation apparatus using the light guide 431 shown in FIG. 1B, the light having a higher intensity is irradiated on the original irradiation area on the original surface, that is, on the original surface shown in FIG. It is possible to irradiate the portion of the width X of
In addition, the light irradiation devices 18, 118, 218, and 318 of the present embodiment (including the above-described modifications) include a plurality of LEDs 32 as a light source unit and light incident from the LEDs 32 in a specific direction. And light guides 31, 131, 231, and 331 made of a translucent material that guides and emits light. The light guides 31, 131, 231, and 331 are incident planes 31 a, 131 a, 231 a, and 331 a on which light from the plurality of LEDs 32 is incident, and are incident on the incident planes that are parallel to the incident plane. It has emission planes 31b, 131b, 231b, and 331b that emit light toward the original surface to be irradiated, and a connection surface that connects the incidence plane and the emission plane. If at least a part 31c, 131c, 131d, 231c, 231d, 331c of the coupling surface is a plane parallel to the normal direction of the incident plane, the angle is smaller than the critical angle α. Orientation is performed so that part or all of incident light that reaches the plane is totally reflected. Thereby, in the light guide 431 shown in FIG. 1B, the incident light that has been transmitted through the connecting surface 431c and has exited the light guide is totally reflected so that it does not exit the light guide. Can be. Therefore, more incident light can be guided to the emission planes 31b, 131b, 231b, and 331b than the light guide 431 shown in FIG. As a result, compared with the light irradiation apparatus using the light guide 431 shown in FIG. 1B, light having a higher intensity is irradiated on the irradiation target area on the original surface, that is, on the original surface shown in FIG. It is possible to irradiate the portion of the width X of
If the at least part 31c, 131c, 131d, 231c, 231d, 331c of the coupling surface is a plane parallel to the normal direction of the incident planes 31a, 131a, 231a, 331a, the critical angle α The incident light that reaches the plane at a smaller angle is the incident plane 31a of the light guide of the light emitted from the LED 32 at an angle larger than the half-value angle γ _{0 of the} light emitted from the plurality of LEDs 32. , 131a, 231a, 331a.
Further, in the light irradiation devices 18, 118, 218, 318 of the present embodiment (including the above-described modifications), the light guides 31, 131, 231, 331 are provided on the incident planes 31a, 131a, 231a, 331a. When viewed from any direction orthogonal to the normal direction, it has a shape with no part from the incident plane toward the exit plane. This makes it easy to take out the molded resin from the mold when manufacturing the light guides 31, 131, 231, and 331 by a resin mold manufacturing method in which a mold is filled with a light-transmitting resin. . As a result, the manufacturing cost can be further suppressed.
In particular, like the light guides 31, 131, and 331 described in the above embodiment and the first and third modifications, the normal of the incident plane so as to pass through the at least part 31c, 131c, 131d, and 331c of the connection surface. The cut surface when cut along the direction is trapezoidal, the surface corresponding to the short side of the trapezoid is the incident plane, and the surface corresponding to the long side of the trapezoid is the output plane If it comprises, it becomes possible to simplify a metal mold | die and can suppress manufacturing cost more.
Further, like the light guides 131 and 231 described in the first and second modifications, the at least portions 31c, 231c, and 231d of the connection surface are surfaces with respect to a specific surface along the normal direction of the incident plane. If it is symmetrical, more light can be collected in the irradiation target area, that is, the portion of the width X on the original surface shown in FIG.
Further, in the light irradiation devices 18, 118, 218, 318 of the present embodiment (including the above-described modifications), all of the light emitted from the plurality of LEDs 32 is incident on the light guides 31, 131, 231, 331. A plurality of LEDs 32 and light guides 31, 131, 231, 331 are arranged so as to be incident on the planes 31a, 131a, 231a, 331a. When a plurality of LEDs 32 are used as the light source unit, it is desirable that all the light emitted from the plurality of LEDs 32 is incident on the light guides 31, 131, 231 because it is relatively difficult to increase the light intensity. . If it does in this way, it will become possible to use the light irradiated from a plurality of LED32 without waste. When the light intensity of the LEDs 32 is sufficiently high, only a part of the light emitted from the plurality of LEDs 32 is prevented from entering the incident planes 31a, 131a, 231a, 331a of the light guides 31, 131, 231, 331. May be.
Further, in the light irradiation devices 18, 118, 218, and 318 of the present embodiment (including the above-described modifications), since a plurality of LEDs (light emitting diodes) 32 are used as the light source unit, power consumption is small, and A light source unit with a small calorific value can be realized.
In the light irradiation devices 18, 118, 218, and 318 of the present embodiment (including the above-described modifications), a light source unit in which LEDs 32 that are a plurality of light sources are arranged in one or a plurality of rows is used. ing. The connecting surface to be oriented is a connecting surface oriented in a direction orthogonal to the column direction of the plurality of LEDs 32 among the connecting surfaces of the light guides 31, 131, 231 and 331. According to this light irradiation device, light can be irradiated to a long region in the column direction of the LED. Therefore, light irradiation means that requires light irradiation to the long region, for example, an image reading device This light irradiation apparatus can be used as the light irradiation means.
In the present embodiment (including the above-described modifications), a light irradiating unit that irradiates light on the document surface and an image reading unit that receives reflected light from the document surface and reads an image on the document surface. In the scanner unit, which is an image reading apparatus including the image reading mechanism 13 as a means, the above-described light irradiation device is used as the light irradiation means. Therefore, according to this scanner unit, it is possible to irradiate the portion with the width X of the document surface with a high intensity even when using a light irradiation device with a low manufacturing cost. As a result, a low-cost scanner unit can be provided.
In this embodiment (including the above-described modifications), an image reading unit that reads an image on a document surface, and an image on a recording sheet S that is a recording material based on image information read by the image reading unit. In the copying machine 1 which is an image forming apparatus including a printer engine 3 as an image forming unit for forming the image, the scanner unit is used as the image reading unit. As a result, a low-cost image forming apparatus can be provided as a result of using a low-cost scanner unit.

In the present embodiment (including the above-described modifications, the same applies hereinafter), the light emitted from the emission plane of the light guide is emitted in a direction substantially parallel to the substrate surface of the LED array substrate 30. However, the light may be emitted in a direction substantially perpendicular to the substrate surface of the LED array substrate 30.
In the present embodiment, the present invention has been described by taking a copying machine as an example. However, the present invention also applies to a single product (scanner) of an image reading apparatus having the same configuration as the image reading unit of the copying machine. The present invention can be applied, and can also be applied to other image forming apparatuses such as a facsimile provided with an image reading unit having the same configuration as the image reading unit of the copying machine or devices other than the image forming apparatus.
In the present embodiment, the case where a plurality of LEDs are used as the LED 32 has been described. However, the present invention can be effectively applied to any other LED 32.

DESCRIPTION OF SYMBOLS 1 Copy machine 3 Printer engine 13 Image reading mechanism 18,118,218,318 Light irradiation apparatus 30 LED array board 31,131,231,331,431,531 Light guide 31a, 131a, 231a, 331a, 431a, 531b Incident Plane 31b, 131b, 231b, 331b, 431b Outgoing plane 31c, 131c, 131d, 231c, 231d, 331c Specific connection surface 32 LED

JP 2004-361425 A

Claims (5)

A substrate which light source is provided on the substrate surface,
A light source unit having an emission surface that radiates light from the light source radially, the emission surface facing a direction along the substrate surface;
In a light irradiation apparatus comprising a light guide made of a translucent material that guides and emits light incident from an emission surface of the light source unit in a specific direction,
The light guide is disposed opposite to the light emission surface of the light source unit and is incident on the light incident surface from which the light emitted from the light emission surface is incident. The light incident from the light incident surface is incident on the document surface. An exit surface that emits toward the surface, and a connection surface that connects the entrance plane and the exit surface;
If this part is a plane parallel to the normal direction of the incident plane at least on the side close to the incident plane of the coupling surface, the plane will reach the plane at an angle smaller than the critical angle. An inclined portion inclined with respect to the normal direction of the incident plane is provided so that a part or all of the incident light is totally reflected,
The light irradiation apparatus, wherein the light guide is disposed so that the incident plane faces both the emission surface of the light source unit and the end surface of the substrate. In the light irradiation apparatus of Claim 1 ,
A light irradiation apparatus, wherein the light guide is arranged so that a center of an incident plane of the light guide is opposed to a center of an emission surface of the light source unit. In the light irradiation apparatus of Claim 1 or 2 ,
The light irradiating apparatus, wherein the light transmissive material constituting the light guide is a resin having a light transmissive property. In an image reading apparatus comprising: a light irradiating unit that irradiates light on a document surface; and an image reading unit that receives reflected light from the document surface and reads an image on the document surface.
As the light irradiation means, the image reading apparatus characterized by using the light irradiation device according to any one of claims 1 to 3. An image reading unit for reading an image on a document surface;
In an image forming apparatus comprising an image forming unit that forms an image on a recording material based on image information read by the image reading unit,
An image forming apparatus using the image reading apparatus according to claim 4 as the image reading section.

Images