JP5787122B2 - Lighting device - Google Patents

Description

  The present invention relates to an image reading apparatus used for a digital copying machine or an image scanner.

In recent years, light emitting diodes (LEDs) have been actively developed, and the brightness of LED elements has been rapidly increased. LEDs generally have advantages such as long life, high efficiency, high G resistance, and monochromatic light emission, and are expected to be applied in many lighting fields.
As one of such applications, an LED is used in a document illumination device of an image reading apparatus such as a digital copying machine or an image scanner.

Various methods have been proposed for using LEDs used in image reading apparatuses. For example, in Patent Document 1, a large number of LEDs are arranged in parallel with the main scanning direction of the document, and the emitted light of the LEDs is diffused without giving an optical action in the main scanning direction, and the reflecting surface in the sub scanning direction. The light condensing action increases the illuminance in the reading target area on the original surface.
In Patent Document 2, light emitted from an LED is guided in the main scanning direction by repeating total reflection in the light guide, diffused / reflected in the diffusion / reflection area, and light that does not satisfy the total reflection condition is guided to the light guide. The method of emitting to the outside is taken. Thereby, the uniformity of illuminance distribution in the main scanning direction is enhanced.
Furthermore, in Patent Document 3, a large number of LEDs are arranged in parallel to the main scanning direction of the document, and the emitted light from the LEDs is diffused without giving an optical action in the main scanning direction, and in the sub-scanning direction, the lens The illuminance in the reading target area on the document surface is increased by the light condensing action.

  However, if a book or the like is opened and placed on the contact glass (original table), the inter-page portion will inevitably float due to the structure of the book or the like. I have it. The portion that floats at this angle cannot be illuminated entirely by illumination from one direction, and a shadow is generated, so that there is a problem that a black shadow is read at the time of document reading.

  Conventionally, in a light source using a cold-cathode tube, as in Patent Document 3, illumination from two directions of a first region and a second region has been realized by placing a counter reflector. Here, the light source side is defined as the first region and the opposite side of the light source is defined as the second region from the light path reflected from the document and used for image formation.

  However, in the case of the configuration described in Patent Document 1, the use efficiency of light can be increased by using the reflection surface, but the document surface can be illuminated only from the first region side. Since the emitted light of the LED is collected on the reflecting surface, even if the counter reflector is installed in the second region, there is almost no light going to the counter reflector, so that illumination from two directions is substantially impossible. Is possible. If the degree of condensing is reduced to enable illumination from two directions, the light utilization efficiency is significantly reduced.

  Further, in the case of the configuration described in Patent Document 2, the number of LEDs that can be installed for one light guide is limited. Therefore, the amount of light emitted from the illumination optical system is absolutely inferior to the method of arranging LEDs. For this reason, with the configuration as described in Patent Document 2, it is desirable to install an illumination optical system in each of the first region and the second region and perform illumination from two directions, but this increases the cost. .

  Further, in the case of the configuration described in Patent Document 3, the size of the entire illumination optical system in the first mirror direction from the document surface tends to be increased.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and can prevent the generation of a shadow portion due to the floating of the original surface, and is small in size and does not weaken the degree of condensing, and has a high light utilization efficiency. An object of the present invention is to provide an apparatus and an image forming apparatus.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an illumination device with high light utilization efficiency that does not weaken the degree of light collection .

The illuminating device according to the present invention provided to solve the above problems specifically has the technical features described in the following (1) to (4) .

(1) An illumination device used in a document reading device, the document reading device reflecting a light source, an optical member having a condensing function, light emitted from the light source and light collected by the optical member. includes a plurality of reflecting members for illuminating a reading target area of the said optical member includes a first reflector and a second reflector which is arranged to be facing each other, said first reflector The plate and the second reflecting plate have a larger distance B between the reflecting surfaces on the light emitting side than the distance A between the reflecting surfaces on the light incident side from the light source, and the first reflecting plate and the second reflecting plate The length from the light source side end of the second reflection plate to the emission side end is longer than the distance B between the reflection surfaces of the first reflection plate and the second reflection plate, and the plurality of reflections. The member illuminates the reading target region from different directions. It is.
(2) The illumination device according to (1), wherein the optical member includes a side reflection plate having a condensing function in a direction different from the first reflection plate and the second reflection plate. It is.
(3) The direction of the reflecting member from the light source is a sub-scanning direction, and the direction perpendicular to the sub-scanning direction and in which the first reflecting plate and the second reflecting plate are not arranged is main scanning. The illumination device according to (2), wherein the optical member includes a side reflection plate at an end portion in the main scanning direction of the first reflection plate and the second reflection plate when the direction is set. It is.
(4) the side reflection plate is disposed opposite one by one, the one pair of opposed side reflector, to the side reflection plates distance C side incident from the light source, the side of the side where light is emitted It is arrange | positioned so that the distance D between reflecting plates may become large, It is an illuminating device as described in said (2) or (3) characterized by the above-mentioned.
(5) The light source is made by arranging a plurality of LED in a predetermined direction, said pair of opposed side reflector, spread in the array direction of the plurality of LED of the light emitted from the plurality of LED The illumination device according to ( 4 ) above, wherein the light to be collected is condensed.

ADVANTAGE OF THE INVENTION According to this invention, the illuminating device of the high light utilization efficiency which does not weaken the degree of condensing can be provided.

1 is a sub-scanning sectional view showing a configuration of a first embodiment according to an image reading apparatus of the present invention. 1 is a main scanning sectional view showing a configuration of a first embodiment according to an image reading apparatus of the present invention; It is the schematic which shows the shortest distance r in which the light radiate | emitted from the light emitting diode reaches | attains a reading object area | region in 1st Embodiment which concerns on the image reading apparatus of this invention. FIG. 3 is a schematic diagram illustrating a path from a reading target area to a CCD in the first embodiment of the image reading apparatus according to the present invention. 1 is a schematic diagram illustrating a configuration of a first embodiment according to an image forming apparatus of the present invention. It is a sub-scan sectional view showing the configuration of the second embodiment according to the image reading apparatus of the present invention. FIG. 5 is a main scanning sectional view showing a configuration of a second embodiment according to the image reading apparatus of the present invention. It is the schematic which shows the shortest distance r 'in which the light radiate | emitted from the light emitting diode reaches | attains a reading object area | region in 2nd Embodiment concerning the image reading apparatus of this invention. It is a sub-scanning sectional view showing the configuration of a third embodiment according to the image reading apparatus of the present invention. It is a main scanning sectional view showing the configuration of a third embodiment according to the image reading apparatus of the present invention. It is a sub-scanning sectional view showing the configuration of a fourth embodiment according to the image reading apparatus of the present invention. FIG. 10 is a main scanning sectional view showing a configuration of a fourth embodiment according to the image reading apparatus of the present invention. FIG. 10 is a main scanning sectional view showing a configuration of an illumination optical system which is a part of a configuration of a fifth embodiment according to the image reading apparatus of the present invention. It is a main scanning sectional view showing a configuration of a modification of the illumination optical system which is a part of the configuration of the fifth embodiment of the image reading apparatus of the present invention. It is a sub-scanning sectional view showing the configuration of a sixth embodiment according to the image reading apparatus of the present invention. FIG. 10 is a main scanning sectional view showing a configuration of a sixth embodiment according to the image reading apparatus of the present invention. It is the schematic which showed the shape of the parabolic opposing reflector in 6th Embodiment which concerns on the image reading apparatus of this invention. FIG. 10 is a sub-scan sectional view showing a configuration of a seventh embodiment according to the image reading apparatus of the present invention.

The basic configuration of the image reading apparatus and the image forming apparatus of the present invention will be described below.
In addition, since embodiment described below is a suitable embodiment of this invention, limitation of the technically preferable various kind is attached | subjected, The range of this invention limits this invention especially in the following description. Unless otherwise stated, the present invention is not limited to these embodiments.

(Image reading device)
An image reading apparatus according to the present invention includes a light source for irradiating light on a document surface, an illumination optical system that guides light emitted from the light source to a reading target region having a length and a width, and the light reflected from the document surface. In the image reading apparatus having an imaging optical system that forms an image of light and a sensor that is provided in an imaging unit of the imaging optical system and reads an image of the document on the document surface, the illumination optical system includes a collecting optical system. An imaginary member having an optical member having a light action and a plurality of reflecting members, wherein a member installation region of the illumination optical system is perpendicular to the document surface and parallel to the length direction and passes through the reading target region. When divided into two sections by a plane, the plurality of reflecting members are installed at least one in each section.

[First Embodiment]
FIG. 1 and FIG. 3 show the configuration (sub-scanning cross section) of the first embodiment according to the image reading apparatus of the present invention, and FIG. 2 shows the configuration of the first embodiment according to the image reading apparatus of the present invention (mainly). Scanning cross section).
As shown in FIGS. 1 and 2, the light source and the illumination optical system in the first embodiment have the following configurations.
(light source)
・ LED4 (× 5)
(Illumination optics)
-Reflector 1-a
-Reflector 1-b
-Reflector 1-c
-Reflector 1-d
・ Reflector 2
・ Reflector 3

(reflector)
Here, the reflecting plates are all flat, and the optical members composed of the reflecting plates 1-a, 1-b, 1-c, and 1-d are integrated by an adhesive. Further, the integrated reflector is referred to as a light guide here.

(Virtual plane, first area, second area)
In FIG. 1, the length direction is a direction perpendicular to the drawing, and the width direction is the left-right direction of the drawing.
The virtual plane is a plane that is perpendicular to the document surface and parallel to the length direction and passes through the reading target region 6. That is, a plane through which light reflected from the original and used for image formation passes is defined as a virtual plane. Further, when the installation area of the light source and the illumination optical system member is divided into two sections by the virtual plane, a section where the light source exists is a first area, and a section where the light source does not exist is a second area.
A specific example in this embodiment will be described with reference to FIG. In FIG. 1, the virtual plane is a line that serves as a boundary between the first region and the second region. The first region includes the LED 4 and the reflectors 1-a, 1-b, 1-c, 1, The optical member made of -d and the reflecting plate 2 are arranged, and the reflecting plate 3 is arranged in the second region.
In the following embodiments, the virtual plane, the first region, and the second region are used in the same definition as in the present embodiment. More specifically, in the arrangement configuration of the virtual plane 7, the first area, and the second area, the configuration is the same as in the present embodiment except that the type of the optical member is changed.

(Configuration of image reading apparatus)
In the sub-scanning direction, the light emitted from the LED 4 is light that diffuses outward from the front direction of the LED 4 out of the light emitted from the LED 4, and the reflecting plate 1-a facing the parallel to the length direction. The light is reflected and condensed in the front direction of the LED 4 by the reflecting plate 1-b. The distance between the reflecting plate 1-a and the reflecting plate 1-b facing each other is larger than the distance A between the reflection plates on the light incident side from the light source, and the distance B between the reflection plates on the light emission side. So that they are arranged with an angle.

  On the other hand, light that diffuses because no optical action is given in the main scanning direction, but the light that escapes to the outside of the reflecting plate 1-a and the reflecting plate 1-b facing each other is reflected by the reflecting plate 1-c and the reflecting plate 1. -D is used to effectively illuminate the original.

  As described above, the light emitted from the light guide made of the reflecting plates 1-a, 1-b, 1-c, and 1-d is reflected by the reflecting plate 2 and guided to the document surface in the first region. In the second area, the light is reflected by the reflecting plate 3 and guided to the original surface.

  Further, it is preferable that the reflecting plate 1-a and the reflecting plate 1-b are arranged at an angle such that the light emission direction is parallel to the document surface.

According to the above configuration, since the light emission direction is parallel to the document surface, the light source and the optical member are arranged parallel to the document surface. Therefore, the thickness of the light source and the illumination optical system member in the direction perpendicular to the document surface (the vertical direction in FIG. 1) is reduced, and as a result, the image reading apparatus can be made compact.
Further, the space required for diffusing the emitted light of the LED (in order to make the illuminance unevenness in the main scanning direction uniform even with a small number of LEDs) is the front direction of the light emitting surface of the LED (left and right direction in FIG. 1). Therefore, as in this embodiment, the light emission direction of the LED 4 is made parallel to the document surface (upper surface of the contact glass 5 in the figure), the light is collected in the sub-scanning direction by the light guide, and the light is lifted by the mirror. With this configuration, a compact configuration can be achieved in the vertical direction of FIG. Naturally, by increasing the number of LEDs from five, it is possible to reduce the size in the left and right direction of FIG. Furthermore, since illumination is performed from two directions, no shadow is produced even if the document is lifted.

  Then, the illuminance distribution in the sub-scanning direction is optimized as shown in FIG. 1 by adjusting the angle of the reflecting plate in consideration of the light distribution of the LED 4, for example, a flat of about 3 mm in the vicinity of the reading target region 6. Adjustment and the like to obtain a proper illuminance distribution can be performed. At this time, by providing the reflecting plate with a curvature, the degree of freedom in design increases, and a more desirable light amount distribution can be formed.

  In obtaining the desired value of the light emitting diode interval P so that there is no illuminance unevenness in the main scanning direction in the reading target region 6, the distance r (the light emitted from the light emitting diode passes through the optical member and is reflected by a plurality of reflecting plates). The shortest distance that is reflected by one of the reflecting plates and reaches the reading target area 6) is required. The distance r can be obtained from the route of FIG. 3 in the first embodiment.

Using the obtained distance r, a desirable value of the light emitting diode interval P that does not cause unevenness in illuminance can be calculated from the following formula 1.
P ≦ 1.3 · r (Formula 1)

  FIG. 4 is a schematic diagram showing a path from the reading target region 6 to the CCD in the first embodiment according to the image reading apparatus of the present invention. The light reflected from the reading target region 6 passes through the virtual plane 7, is reflected by a plurality of folding mirrors, and is guided to a reading lens. Further, the light passing through the reading lens is guided to the CCD, and image information is read by the CCD.

(Image forming device)
FIG. 5 is a schematic diagram of an image forming apparatus provided with the image reading apparatus of the present invention.
In the figure, reference numeral 100 denotes an image forming apparatus, and 200 denotes an image reading apparatus. Other symbols are directly cited in the description.

  In the image reading apparatus 200, the document 202 is placed on the contact glass 5, and the document 202 is illuminated by an illumination unit (not shown) mounted on the first traveling body 203 placed below the contact glass 5. The reflected light from the document 202 is reflected by the first mirror 203 a of the first traveling body 203, and then reflected by the first mirror 204 a and the second mirror 204 b of the second traveling body 204 and guided to the reduction imaging lens 205. The image is formed on the line sensor 206. In the case of a color image reading apparatus, the present invention can be applied with the same configuration by providing the line sensor 206 for each color of RGB.

When reading the longitudinal direction of the document, the first traveling body 203 moves to the right in the figure at a speed of V, and at the same time, the second traveling body 204 moves to the right at a speed 1/2 V that is half that of the first traveling body 203. , The optical path length from the document 202 to the line sensor 206 is kept constant, and the entire document can be read at a constant magnification.
Usually, as a method of using LEDs as a document illumination device used in an image reading apparatus, a large number of LED elements are arranged and used in an array.

  The image forming apparatus 100 includes a drum-like latent image carrier 111, and a charging roller 112, a developing device 113, a transfer roller 114, and a cleaning device 115 as a charging unit are disposed around the latent image carrier 111. A “corona charger” can also be used as the charging means. Further, an optical scanning device 117 that receives document information from the outside such as an image reading unit and performs optical scanning with the laser beam LB is provided, and “exposure by optical writing” is performed between the charging roller 112 and the developing device 113. To do.

  When image formation is performed, the latent image carrier 111, which is a photoconductive photosensitive member, is rotated at a constant speed in the clockwise direction, and the surface thereof is uniformly charged by the charging roller 112, and the light of the laser beam LB of the optical scanning device 117 is obtained. An electrostatic latent image is formed upon exposure by writing. The formed electrostatic latent image includes a so-called negative latent image in which an image portion is exposed and a so-called positive latent image in which a non-image portion is exposed. Any of the above electrostatic latent images is visualized by the developing device 113 using the electrostatic latent image developing toner. At this time, by providing a total of four developing devices 113 for each of the four colors of YMCK, an image forming apparatus capable of forming a color image is obtained.

  The cassette 118 storing the transfer paper P is detachable from the main body of the image forming apparatus 100. When the transfer paper P is mounted as shown in the drawing, the uppermost sheet of the stored transfer paper P is fed by the paper supply roller 120. The leading edge of the fed transfer paper P is caught by the registration roller pair 119. The registration roller pair 119 feeds the transfer paper P to the transfer unit at the timing when the toner image on the latent image carrier 111 moves to the transfer position. The transferred transfer paper P is superimposed on the toner image at the transfer portion, and the toner image is electrostatically transferred by the action of the transfer roller 114. The transfer paper P to which the toner image is transferred is sent to the fixing device 116, where the toner image is fixed by the fixing device 116, passes through the conveyance path 121, and is discharged onto the tray 123 by the discharge roller pair 122. The surface of the latent image carrier 111 after the toner image is transferred is cleaned by a cleaning device 115 to remove residual toner, paper dust, and the like.

[Second Embodiment]
6 and 8 show the configuration (sub-scanning cross section) of the second embodiment of the image reading apparatus of the present invention, and FIG. 7 shows the configuration of the second embodiment of the image reading apparatus of the present invention (mainly). Scanning cross section).
As shown in FIGS. 6 and 7, the light source and the illumination optical system in the second embodiment have the following configuration.
(light source)
・ LED4 (× 5)
(Illumination optics)
・ Light guide 8
・ Reflector 2
・ Reflector 3

(Reflector, light guide)
Here, the reflectors are all flat, and the configuration other than the light guide 8 is the same as that of the first embodiment. The difference between the light guide 8 of the first embodiment and the second embodiment will be described below.

  In the light guide of the first embodiment, the reflective surface of an inexpensive reflector is usually mirror-finished with an aluminum coat or the like, so that the reflectance is approximately 90% with visible light. On the other hand, the light guide 8 of the second embodiment is made of a material such as glass or plastic and uses total reflection of light. Therefore, the reflectance is almost 100%. Here, the reflection surface of the light guide body 8 of the second embodiment is made into a mirror surface state with less roughness by carrying out a polishing process, whereby the reflectance becomes closer to 100%. When the reflecting surface is rough, the loss on the surface increases. The light guide 8 is preferably made of plastic rather than glass because it is easy to process and can be reduced in weight.

  The light guide 8 according to the second embodiment is composed of six planes. The light incident surface (the surface closest to the LED 4 in FIG. 6) and the light output surface (the closest to the reflector 2 in FIG. 6). The surface) is a surface on which light is incident and emitted without using total reflection of light. Therefore, there is no problem if the surface shape is not limited to a flat surface but has high light utilization efficiency. Therefore, it can be said that the light guide 8 only needs to have at least four planes using total reflection.

  Two of the four planes are arranged to face each other, and the two faces arranged to face each other are planes on the side from which light is emitted with respect to the inter-plane distance A ′ on the side from which light enters from the light source. It arrange | positions so that the distance B 'may become large.

Moreover, it is preferable that the two surfaces arranged opposite to each other are arranged in parallel in the length direction.
With the above configuration, in the sub-scanning direction, the light emitted from the LED 4 efficiently reflects and collects the light emitted from the LED 4 that diffuses outward from the front direction of the LED 4 in the front direction of the LED 4. Can be lighted.

Further, it is preferable that, of the four planes, other than the two opposed surfaces are arranged perpendicular to the document surface and parallel to the length direction.
With the above configuration, in the main scanning direction, the light that escapes to the outside of the two surfaces arranged opposite to each other can be folded back and used effectively for illuminating the document.

In determining the desirable value of the light emitting diode interval P ′, the distance r ′ (converted distance represented by the following formula 3)
r ′ = r−Σ {Di · (1-1 / Ni)} (Formula 3)
Is required. The distance r ′ can be obtained from the route of FIG. 8 in the second embodiment.
Using the obtained distance r ′, a desirable value of the light-emitting diode interval P ′ that does not cause unevenness in illuminance can be calculated from the following formula 2.
P ′ ≦ 1.3 · r ′ (Formula 2)

  In this case, the difference from the first embodiment is that light passes through a medium (light guide 8) having a refractive index. From the refractive index of the light guide 8 and the path of FIG.

[Third Embodiment]
Configuration of the third embodiment according to the image reading apparatus of the present invention in FIG. 9 (sub-scanning cross-section), the configuration of the third embodiment according to the image reading apparatus of the present invention in FIG. 10 (a main scanning cross-section) Indicates.
As shown in FIGS. 9 and 10, the light source and the illumination optical system in the third embodiment have the following configurations.
(light source)
・ LED4 (× 5)
(Illumination optics)
・ Reflector 9
・ Reflector 2
・ Reflector 3

(Reflector, reflector)
Here, the reflectors are all flat, and the configuration other than the reflector 9 is the same as that of the first embodiment. Since the function of the reflector 9 is the same as that of the light guide of the first embodiment, the reflector 9 will be described below.

  The reflector 9 has a cylindrical surface that has a curvature in the sub-scanning direction and has no curvature in the main scanning direction. The shape of the curved surface is a spherical surface or a paraboloid, and has the effect of making the light emitted from the LED 4 substantially parallel light in the sub-scanning direction.

[Fourth Embodiment]
Construction of a fourth embodiment according to the image reading apparatus of the present invention in FIG. 11 (sub-scanning cross-section), the configuration of the fourth embodiment according to the image reading apparatus of the present invention in FIG. 12 (a main scanning cross-section) Indicates.
Moreover, as shown in FIGS. 11 and 12, the light source and the illumination optical system in the fourth embodiment have the following configurations.
(light source)
・ LED4 (× 5)
(Illumination optics)
・ Lens 10
・ Reflector 2
・ Reflector 3

(Reflector, lens)
Here, the reflecting plates are all flat, and the configuration other than the lens 10 is the same as that of the first embodiment. Since the function of the lens 10 is the same as that of the light guide of the first embodiment, the lens 10 will be described below.

  The lens 10 has a cylindrical surface that has a curvature in the sub-scanning direction and does not have a curvature in the main scanning direction. The shape of the curved surface is a spherical surface or a paraboloid, and has the effect of making the light emitted from the LED 4 substantially parallel light in the sub-scanning direction.

[Fifth Embodiment]
In the fifth embodiment, only the configuration of the illumination optical system in the first embodiment is changed. The configuration of the side reflector and its effect will be described in detail based on the configuration of the fifth embodiment shown in FIGS.

FIG. 13 shows the configuration of the image reading apparatus in FIG. 2 with the reflection plate 2 and the reflection plate 3 omitted in order to clarify the effect of the side reflection plate (reflection plate 1-d). It is only omitted in the drawing, and in the present embodiment, it is an apparatus configuration including the reflecting plate 2 and the reflecting plate 3 as in FIG.
As shown in FIG. 13, the light emitted from the LED and spreading in the main scanning direction is reflected by the side reflector (reflector 1-d) and guided to the reading target region, thereby illuminating light. It is effectively used.

FIG. 14 shows an example in which this side reflector (reflector 1-d) is used more functionally. As shown in FIG. 14, the distance between the reflecting plate 1-c (side reflecting plate) and the reflecting plate 1-d (side reflecting plate) facing each other is the distance C between the side reflecting plates on the side where light enters from the light source, The distance D between the side reflectors on the side from which light is emitted is arranged with an angle so that the relationship C <D is satisfied.
Two effects can be obtained by facing the reflecting plate 1-c and the reflecting plate 1-d facing each other with an angle, rather than facing each other in parallel with the front. One is that the angle of light incident on the reading target region (contact glass that is in close contact with the reading target region) becomes closer to vertical, so that loss due to reflection of light on the contact glass surface is reduced (on the glass surface, (In general, as the angle of light incident on the glass surface becomes steeper, the amount of light reflected on the surface increases and the illumination efficiency (light utilization efficiency) decreases.) . Therefore, it can be expected that light emitted from the LED is used as illumination light for reading, that is, light use efficiency is improved. The other is that by adjusting the angle, as shown in FIG. 14, an improvement in the amount of light at the end of the reading target area can be expected.

[Sixth Embodiment]
FIG. 15 shows the configuration (sub-scanning section) of the sixth embodiment according to the image reading apparatus of the present invention, and FIG. 16 shows the configuration (main scanning section) of the sixth embodiment according to the image reading apparatus of the present invention. Indicates.
In the sixth embodiment, the shape of the opposing reflectors 1-a ′ and 1-b ′ in the first embodiment is set to a parabolic shape. The reflector is parabolic in the length direction and has no curvature in the width direction. As is apparent from FIG. 15, the reflector is parabolic on the sub-scan section, and the light source is placed at or near the focal point of the paraboloid so that the light emitted from the light source is reflected on the reflective surface. The light becomes substantially parallel light.

FIG. 17 shows the line segment of the reflecting surface extended and intersected on the sub-scan section. Naturally, the focal point of the parabola is closer to the light emission direction than the intersection of the line segments (to the right in the figure), so the light source is installed closer to the light emission direction than the intersection of the line segments.
When the reflecting surface is made parabolic like the fifth embodiment, the light emitted from the light source becomes closer to parallel light than the first embodiment, so that the light utilization efficiency is increased, but the reflection is increased. Making the surface parabolic increases the manufacturing cost compared to a flat surface. Therefore, in consideration of the manufacturing cost, a method of setting a plane at an angle approximated to a parabola may be taken.

Further, based on the technical idea of making the reflecting surfaces of the reflecting plates facing each other in a parabolic shape in this embodiment, the reflecting surface of the light guide can be made parabolic, and a parabolic reflecting surface was used. It has been confirmed that the light guide also has the same effect as the present embodiment.
Further, by combining the invention in which the reflecting surface of the light guide is parabolic with the technical idea regarding the arrangement of the side reflectors in the fifth embodiment, it is possible to improve the light utilization efficiency. . In other words, the side planes are placed one by one at both ends in the lengthwise direction of the two faces arranged opposite to each other, and the pair of opposite side planes represents the distance between the side planes on the side incident from the light source as C. It has been confirmed that it is excellent in light utilization efficiency that it is arranged at an angle so that the relationship of C ′ <D ′ is established, where “and the distance D between side planes on the light emitting side”. .

[Seventh Embodiment]
FIG. 18 shows the configuration (sub-scan section) of the seventh embodiment of the image reading apparatus of the present invention.
In the seventh embodiment, the reflecting plate 2 and the reflecting plate 3 in the first embodiment are curved to form a reflecting plate 2 ′ and a reflecting plate 3 ′. By making the reflecting plate a curved surface, the reflecting plate 2 ′ and the reflecting plate 3 ′ can also carry out the light condensing action that only the reflecting plates 1-a and 1-b have in the first embodiment. This can be expected to improve the illuminance of the reading target area.
However, with such a configuration, the illuminance distribution in the sub-scanning direction becomes narrower in a region where the illuminance is uniform. Accordingly, when the illumination area and the reading target area are shifted due to a manufacturing error or the like, there is a concern that the illuminance of the reading target area may be significantly reduced. However, if the manufacturing process is stable and there is no need for such a concern, the configuration of the seventh embodiment is desirable.

  According to the image reading apparatus and the image forming apparatus of the first to seventh embodiments, it is possible to prevent the occurrence of a shadow portion due to floating of the document surface, and it is small and does not weaken the degree of light collection. High light utilization efficiency is possible.

1-a, 1-b, 1-c, 1-d Reflector 2 Reflector 3 Reflector 4 LED
5 Contact Glass 6 Reading Target Area 7 Virtual Plane 8 Light Guide 9 Reflector 10 Lens

JP 2005-241681 A Japanese Patent No. 2693098 JP 2004-361425 A

Claims (5)

An illumination device used for a document reading device,
A light source;
An optical member having a light collecting action;
A plurality of reflecting members that illuminate the reading target area of the document reading apparatus by reflecting the light emitted from the light source and the light collected by the optical member;
The optical member includes a first reflecting plate and a second reflecting plate arranged so as to face each other, and light from the light source enters the first reflecting plate and the second reflecting plate. The distance B between the reflecting surfaces on the side from which light is emitted is larger than the distance A between the reflecting surfaces on the side,
The length from the light source side end to the exit side end of the first reflecting plate and the second reflecting plate is the distance B between the reflecting surfaces of the first reflecting plate and the second reflecting plate. Longer than
The plurality of reflecting members illuminate the reading target region from different directions. The lighting device according to claim 1, wherein the optical member includes a side reflection plate having a light collecting action in a direction different from the first reflection plate and the second reflection plate . The direction from the light source to the reflecting member is the sub-scanning direction, and the direction perpendicular to the sub-scanning direction and in which the first reflecting plate and the second reflecting plate are not arranged is the main scanning direction. When
The lighting device according to claim 2, wherein the optical member has a side reflection plate at an end portion in the main scanning direction of the first reflection plate and the second reflection plate. The back reflector is placed opposite one by one,
The pair of side reflectors facing each other are arranged such that the distance D between the side reflectors on the side from which light is emitted is greater than the distance C between the side reflectors on the side from which the light source is incident. The lighting device according to claim 2 or 3 . The light source is formed by arranging a plurality of LEDs in a predetermined direction,
5. The lighting device according to claim 4 , wherein the pair of side reflectors facing each other collects light diffused in an arrangement direction of the plurality of LEDs out of light emitted from the plurality of LEDs .

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