JP2013090268A - Original illumination unit, original reading device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an original illumination unit excellent in illuminance surface smoothness in a main scan direction, capable of realizing reduction in thickness and suppressing halation due to illumination light; an original reading device having a small size and excellent in stability in a reading property; and an image forming device.SOLUTION: An original illumination unit at least comprises a light source 1, a light guide body 5 and a counter reflection member 10. The light guide body 5 has a shape thin in a normal direction of an original platen 4, and has an internal reflection area 13 and an orientation control area 14 on an inner surface opposing to the original platen 4. In the unit, the light guide body 5 is arranged in such a manner that a position of a reading area side end 19 of the orientation control area 14 becomes a position more apart from a reading optical axis 11 than a first halation line LA with respect to the first halation line LA which is a line of a light beam path extended from a reading area 12 to a direction in which the light guide body 5 is set, and which has an angle with respect to the normal line of the original platen 4 being an angle which is a standard of generation of halation. An original reading device and an image forming device including the original illumination unit are provided.

Description

  The present invention relates to a document illumination unit used in a reading device such as a digital copying machine or an image scanner, an image reading device including the document illumination unit, a copying machine including the image reading device, a printer, a facsimile, a plotter, and the like. The present invention relates to an image forming apparatus such as a multifunction machine including at least one of the above.

In recent years, development of light emitting diodes (hereinafter referred to as LEDs) has been actively conducted. The brightness of the LED element is rapidly increasing, and the cost is decreasing. LEDs generally have advantages such as long life, high efficiency, high impact resistance, and monochromatic light emission, and are expected to be applied in many lighting fields.
One of the applications is a document illumination device of an image reading device such as a digital copying machine or an image scanner. Further, the emission spectrum of the white light emitting LED element covers the visible wavelength band, and can be used for a document illumination apparatus of a color image reading apparatus. For this reason, a wide variety of document illumination devices using white LEDs have been proposed.

  A reading illumination system using an LED as a light source includes a method in which a light beam emitted from a light source is propagated using a light guide to irradiate a document surface. There is known a method in which the light guide is arranged to be inclined with respect to an original reading surface (hereinafter also referred to as “original surface”) of the original table. It becomes difficult to make thin in the vertical direction.

In document reading, when a book or the like is opened and placed on a document table, the inter-page portion is structurally lifted and has an angle with respect to the document table, and illumination from one direction cannot illuminate the whole. There is a problem that a shadow is formed and a black shadow is read. Similarly, the cut and pasted document also has a problem that a shadow line is generated at the document step portion during reading.
In order to avoid these problems, it is known to perform illumination from both sides with the reading optical axis in between.

As a configuration for illuminating the document from both sides, for example, a first illuminating unit that guides the radiated light from the light source to the illumination region, and a second unit that illuminates the first unit from the side sandwiching the reading optical axis. A configuration of an illumination system including an illumination unit is known, and in this configuration, a part of light from the first illumination unit is guided to the second illumination unit and reflected by the second illumination unit to the illumination area. A method for guiding light is known (see, for example, Patent Documents 1 and 2).
Patent Documents 1 and 2 describe that a light guide (hereinafter, also referred to as “light guide plate”) is used as the first illumination unit, and that the optical path is separated in the light guide.

The configuration of the illumination system of Patent Document 1 is shown in FIG. In the illumination system of Patent Document 1, in order to guide light from the first illumination means in the direction of the illumination area, it is necessary to dispose a part of the reflection surface constituting the light guide plate with respect to the document table. (Inclined reflecting surface indicated by 223e). By optimizing the position and angle of the inclined reflecting surface 223e, the light from the light source is guided toward the illumination area.
The configuration of the illumination system of Patent Document 2 is shown in FIG. The light guide plate in the illumination system of Patent Document 2 also has an inclined reflection surface. Note that the light guide plate of Patent Document 2 has a thick light guide plate because the exit surface protrudes toward the document table.

In the configuration of the illumination system described in Patent Documents 1 and 2, the light emitted from the LED spreads in the main scanning direction. Although it is subjected to the effect of internal reflection inside the light guide, the characteristic spreading in the main scanning direction remains even after it is emitted from the light guide.
Further, since the light emitting body is arranged so as to have a certain distance from the light exit surface to the illumination area, the light of adjacent LEDs is superimposed in the main scanning direction in the illumination area, and the illuminance distribution in the main scanning direction Flatness is improved.

  In order to make the illumination system thin, when the light guide having an inclined reflection surface as described in Patent Documents 1 and 2 is made thin, the length of the inclined reflection surface in the thickness direction of the light guide plate is inevitably also. It becomes shorter and its area decreases. Then, the light directly propagated from the light source to the inclined reflecting surface is reduced, and the amount of light that can be guided to the illumination area is reduced, which makes it difficult to secure necessary illuminance.

  In addition, for example, when reading is performed in a state where the document is lifted from the document table, a light beam illuminated from the light guide plate and regularly reflected in the reading region reaches the image sensor, and the document density is partially increased, and the image is Whitening halation may occur. In a reading apparatus using an LED light source, a part of an original becomes an image with overexposed dots.

  As a method for suppressing such halation, a method of adding a diffuser plate in the illumination optical path to make the light quantity in the reading region uniform can be considered. However, there is a problem that increasing the number of diffusing members such as a diffusing plate increases the cost and prevents the illumination system from being thinned.

SUMMARY OF THE INVENTION In view of the above problems, the present invention has an object to provide a document illumination unit that can be reduced in thickness, can suppress the occurrence of halation due to illumination light, and has excellent illuminance flatness in the main scanning direction. And
Another object of the present invention is to provide a document reading apparatus and an image forming apparatus which are provided with the document illumination unit and which are small in size and excellent in stability of reading performance.

In order to solve the above-described problem, a document illumination unit according to the present invention includes:
In a document illumination unit in a document reading apparatus that irradiates light to a reading region of a document placed on a document table and reads reflected light from the document by an image reading element,
A plurality of light sources arranged in a line in the main scanning direction, an incident surface on which illumination light from the light source is incident, a first emission surface that irradiates the read illumination area with the incident illumination light, and the first emission A light guide having a second emission surface that irradiates in a direction different from the surface, and at least an opposing reflection member that guides the emitted light from the second emission surface of the light guide to the reading region,
The light guide is thin in the normal direction of the document table, and reflects the incident light from the light source on the inner surface facing the document table to propagate the light guide to the first surface. An internal reflection region that leads to the second exit surface, and an orientation control region that deflects the traveling angle of the light beam propagating inside the light guide to irradiate the reading region from the first exit surface,
For a first halation line that is a line of a light path from the reading area in the direction in which the light guide is installed, and an angle with respect to a normal line of the document table is a reference angle for occurrence of halation, The light guide is arranged so that the position in the sub-scanning direction of the reading region side end of the orientation control region is positioned farther from the optical axis of the reading region than the first halation line. This is a featured document illumination unit.

In order to solve the above-described problem, a document reading apparatus according to the present invention includes:
The document illumination unit;
A reading optical system disposed on an optical path of reflected light from a document irradiated with illumination light from the document illumination unit;
An original reading apparatus comprising: an image pickup device on which light incident through the reading optical system is incident.
In order to solve the above problems, an image forming apparatus according to the present invention provides:
The document reading device;
An image forming apparatus comprising: means for forming an image on a recording medium based on image information read by the document reading apparatus.

According to the document illumination unit according to the present invention, it is possible to provide a document illumination unit that can be reduced in thickness, can suppress the occurrence of halation due to illumination light, and has excellent illuminance flatness in the main scanning direction. it can.
Further, it is possible to provide a document reading apparatus and an image forming apparatus which are provided with the document illumination unit and which are small in size and excellent in reading performance.

It is a schematic sectional drawing which shows one embodiment of the original illumination unit of this invention. It is a schematic diagram which shows an example of the reflection in the inside of a light guide of the light ray which injected into the light guide. It is the schematic explaining the document illumination unit which concerns on the 3rd and 5th embodiment. It is the schematic explaining the document illumination unit which concerns on a 4th embodiment. It is the schematic explaining the document illumination unit which concerns on a 7th embodiment. It is the schematic explaining the document illumination unit which concerns on a 9th embodiment. It is a figure explaining the height of the intersection of a halation line and a document reading surface. 1 is a schematic sectional view showing an embodiment of a document reading apparatus according to the present invention. It is a schematic sectional drawing which shows the other embodiment of the original document reading apparatus concerning this invention. 1 is a schematic cross-sectional view showing an embodiment of an image forming apparatus according to the present invention. It is a figure which shows a prior art example. It is a figure which shows a prior art example.

Hereinafter, a document illumination unit, a document reading device, and an image forming apparatus according to the present invention will be described with reference to the drawings. The present invention is not limited to the embodiments described below, and other embodiments, additions, modifications, deletions, and the like can be changed within a range that can be conceived by those skilled in the art, and any aspect is possible. As long as the functions and effects of the present invention are exhibited, the scope of the present invention is included.
In the drawings describing the following embodiments, the main scanning direction is the X direction, the sub-scanning direction (document reading direction) is the Z direction, and the X direction and the direction orthogonal to the Z direction are the Y direction.

[First Embodiment]
FIG. 1 is a schematic sectional view showing one embodiment of the document illumination unit of the present invention.
The document illumination unit of the present invention is a document illumination unit in a document reader that irradiates light to a document reading area 12 placed on a document table 4 and reads reflected light from the document by an image reading element. At least a plurality of light sources 1, a light guide 5, and an opposing reflection member (opposing reflection mirror) 10 are provided.

Since the plurality of light sources 1 are mounted on a substrate (not shown) and are spaced apart from each other at a predetermined interval in the main scanning direction, the normal direction (Y direction) of the document table 4 does not increase.
Light is emitted from the light emitting surface 2 of each light source 1. It arrange | positions so that the normal line direction of the light emission surface 2 may turn into a subscanning direction (Z direction).
As the light source 1, an LED can be used. By using the side view type, the LED mounting substrate can be arranged in the horizontal direction with respect to the document table 4. Therefore, it is preferable to select the side view type from the viewpoint of reducing the thickness of the apparatus. However, the top view type can be used depending on applications and specifications.

The light guide 5 has a thin shape in the Y direction, and the upper horizontal surface 8 and the lower horizontal surface 9 of the light guide 5 are arranged so as to be horizontal with the document table 4. Also, the installation space in the Y direction is thin and small.
The thickness of the light guide plate in the Y direction is about 1 mm, which is smaller than the thickness of the conventional light guide plate (about 4 to 5 mm).

As shown in FIG. 1, the incident surface 3 of the light guide 5 is disposed close to and opposed to the light emitting surface 2 of the light source 1, and from the light incident surface 3 of the light emitted from the light emitting surface 2 of the light source 1. Incidence efficiency to the light guide 5 is high.
As shown in FIG. 1, an alignment control region 14 is provided on the lower horizontal surface 9 of the light guide 5 on the side close to the optical axis (reading optical axis) 11 of the reading region.

FIG. 2 shows an example of reflection inside the light guide of the light beam incident on the light guide 5 from the incident surface 3.
As shown in FIG. 2, the light incident on the orientation control region 14 is reflected to the upper horizontal plane 8 side by the reflection action of the orientation control surface 15 periodically formed in the sub-scanning direction on the orientation control region 14, and the reflection angle. Due to the deflection action, the light is refracted and transmitted through the upper horizontal surface 8 and guided to the reading region 12.
The side far from the reading optical axis 11 of the lower horizontal plane 9 is an internal reflection region 13, and the light incident on the internal reflection region 13 is simply reflected without being deflected by the reflection angle, and the light guide 5 It propagates inside and reaches the second exit surface 7.

As shown in FIG. 2, the reflection action and the deflection action by the internal reflection region 13 and the orientation control region 14 are such that the orientation of the normal line 16 of the orientation control surface 15 of the orientation control region 14 is changed from the orientation of the normal line 17 of the lower horizontal surface 9. Is also obtained by tilting toward the side where the light source 1 is disposed.
In addition, as shown in FIG. 2, the orientation control surface 15 is configured periodically in the sub-scanning direction (Z direction) in the orientation control region 14, thereby shortening the orientation control surface having a predetermined inclination in the sub-scanning direction. At the same time, it can be shortened in the vertical direction (Y direction) of the document table.

  As described above, the light is guided in the direction of the document reading region 12 by the orientation control region 14, but the orientation control region 14 is shifted from the document reading region 12 in the sub-scanning direction as shown in FIG. Yes, the positional relationship is different from the backlight illumination. For this reason, efficient illumination cannot be realized even if the direction in which the orientation becomes strong like the backlight illumination is the Y-axis direction. Here, the orientation ratio in the direction of the document reading area 12 is made high.

Further, the distance from the orientation control region 14 to the document reading region 12 is longer than the distance from the illumination system to the liquid crystal display unit in the backlight illumination device. Since the distance from the reflection at the orientation control area 14 to the document reading area 12 is long, the light flux having an angle width in the main scanning direction also spreads in the main scanning direction. Further, since the light sources 1 are arranged adjacent to each other in the main scanning direction, the light beams from the adjacent light sources 1 are illuminated in the reading region 12 so as to overlap each other. Therefore, the illumination flatness in the main scanning direction is easily obtained as compared with the backlight illumination.
In the case of backlight illumination, the distance to the illumination area is short, and in order to obtain illuminance flatness in the main scanning direction, it is necessary to allow the light flux to spread in the main scanning direction on the orientation control surface. As a periodic structure, it is necessary to form a curved surface in which the inclination of the orientation control surface changes in the main scanning direction, and the structure becomes complicated.
However, on the orientation control surface 14 in the document illumination unit of the present invention, depending on the arrangement pitch of the LED light sources 1 in the main scanning direction, the illuminance in the main scanning direction can be reduced without spreading the light flux in the main scanning direction on the orientation control surface 14. Since flatness is obtained, a continuous surface may be used, and it is not necessary to have a periodic structure in the main scanning direction. The structure can be simpler than that of backlight illumination, and the manufacturing is easy and the cost can be reduced.

When the light guide 5 is disposed at a position close to the reading optical axis 11, halation occurs for the following reason.
Light rays from the orientation control region 14 to the reading region 12 are specularly reflected or diffusely reflected on the original reading surface (18 shown in FIG. 7 and the like). When the specularly reflected light reaches the image sensor via the reading optical system, the light intensity thereof is stronger than that of the diffusely reflected light, and thus halation occurs, resulting in a white image.
Such a phenomenon occurs when the document reading surface is inclined with respect to the document table, such as a book document.

  An angle at which halation occurs can be set in advance, and a halation line serving as a reference for halation occurrence can be defined. That is, a ray path line from the reading area 12 in the direction in which the light guide 5 or the opposing reflection member 10 is installed, and an angle of the ray path line with respect to the normal of the document table 4 is a reference for occurrence of halation. The halation line is defined as the angle that becomes. Hereinafter, the halation line heading in the installation direction of the light guide 5 is referred to as a first halation line, and the halation line heading in the installation direction of the opposing reflection member 10 is referred to as a second halation line.

In order to avoid the occurrence of halation, the position in the sub-scanning direction of the reading area side end of the orientation control area is farther from the optical axis of the reading area than the first halation line with respect to the halation line. It is necessary that the light guide is disposed so as to be positioned.
In order to avoid the occurrence of halation, as shown in FIG. 1, it is necessary to provide the light guide 5 at a position away from the halation line LA with respect to the reading optical axis 11 in the sub-scanning direction. The alignment control region 14 is provided so that the position of the end portion on the side of the reading optical axis 11 is away from the halation line LA.
The angle formed by the light beam reaching the original reading surface from a position farther from the reading optical axis 11 than the end of the orientation control region 14 on the reading optical axis 11 is the normal line of the original table 4. Since the light beam reaching the reading surface is larger than the angle formed with the normal line of the document table 14, halation does not occur unless a light beam closer to the reading optical axis 11 than the end on the reading optical axis 11 side reaches the image sensor.

  Thus, according to the document illumination unit of the present invention, it is possible to avoid the occurrence of halation due to illumination light from the light guide 5 side corresponding to the inclination angle of the document reading surface 18 with a thinner configuration than the conventional one.

[Second Embodiment]
Even when the opposing reflecting member (opposing illumination mirror) 10 is arranged at a position close to the reading optical axis 11, halation occurs for the following reason.
The light beam from the counter illumination mirror 10 to the reading area 11 is also reflected by the document reading surface 18. The reflected light on the document reading surface 18 includes regular reflection light and diffuse reflection light. When the specularly reflected light reaches the image sensor via the reading optical system 20, the intensity of the light is higher than that of the diffusely reflected light, so that halation occurs and the image becomes white. In order to avoid this, as shown in FIG. 1, it is preferable to provide the position of the counter illumination mirror 10 at a position away from the halation line LB with respect to the reading optical axis 11 in the sub-scanning direction. It is preferable that the counter illumination mirror 10 is provided so that the position of the end portion on the reading optical axis side is a position away from the halation line LB.

The angle formed by the light beam reaching the original reading surface from a position farther from the reading optical axis 11 than the reading optical axis 11 side end of the counter illumination mirror 10 is the normal line of the original table 4 from the reading optical axis 11 side end to the original. Since the light beam reaching the reading surface is larger than the angle formed with the normal line of the document table 14, halation does not occur unless a light beam closer to the reading optical axis 11 than the end on the reading optical axis 11 side reaches the image sensor.
According to this embodiment, it is possible to prevent both halation due to illumination light from the light guide 5 and halation due to illumination light from the counter illumination mirror 10.

[Third Embodiment]
As shown in FIG. 3, when the inclination angle of the normal line of the document reading surface 18 with respect to the normal line of the document table 4 is ψ, the first halation line LA is 2 with respect to the normal line of the document table 4. This is a line of a light beam path from the center in the sub-scanning direction of the reading area 12 toward the direction in which the light guide 5 is installed with an angle of × ψ.
In this way, by defining the halation line LA, the light guide 5 and the orientation control region 14 can be appropriately arranged according to the design specifications of how much the inclination of the document reading surface 18 is considered. , Can prevent the occurrence of halation.

As shown in FIG. 3, when the inclination of the document reading surface 18 is ψ, the light beam on the halation line LA incident on the document reading surface 18 at an incident angle of 2ψ is regularly reflected by the document reading surface 18. Since the light reaches the image sensor via the reading optical system 50 as reflected light parallel to the reading optical axis 11, halation occurs.
Therefore, as shown in FIG. 3, if the orientation control region 14 is located farther from the reading optical axis 11 in the sub-scanning direction than the halation line LA, the center of the reading region of the document reading surface 18 from the orientation control region 14 Since any incident light reaching the angle of incidence is greater than 2ψ, it will not be reflected and reflected in a direction parallel to the reading optical axis 11 to cause halation.
In FIG. 3, in order to simplify the explanation, the light refraction at the boundary between the original glass surface 4 and the light guide 5 and the air layer is ignored, but it is desirable to consider these as well. .

  The height h of the intersection between the halation line LA and the document reading surface 18 can be determined as appropriate from the shape of the document reading surface 18 as shown in FIG.

[Fourth Embodiment]
In order to prevent halation from occurring even when the reading optical axis 11 is displaced in the sub-scanning direction due to an assembly error or vibration, a halation line is formed in consideration of the amount of deviation of the reading optical axis 11 in the sub-scanning direction. It is preferable to specify.
As shown in FIG. 4, when a reading area 12 is defined in the sub-scanning direction with the reading optical axis 11 in between, and the inclination angle of the normal of the document reading surface 18 with respect to the normal of the document table 4 in the sub-scanning section is ψ. In addition, it is preferable to define the halation line LA as a light ray path that propagates in the sub-scanning direction in the reading region 12 from the document surface end on the light guide 5 side toward the light guide installation direction at an angle of 2 × ψ.
By defining in this way, even when the reading optical axis 11 is shifted to the position 11 ′, it is possible to avoid the occurrence of halation due to the illumination light from the light guide 5 side.

[Fifth Embodiment]
When the inclination angle of the normal line of the document reading surface 18 with respect to the normal line of the document table 4 is −ψ, the second halation line LB has an angle of −2 × ψ with respect to the normal line of the document table 4. This is a ray path line from the center of the reading area 12 in the sub-scanning direction toward the direction in which the counter illumination mirror 10 is installed.
In this way, by defining the halation line LB, the counter illumination mirror 10 can be appropriately arranged according to the design specification of how much the inclination of the document reading surface 18 is taken into consideration, and the occurrence of halation is prevented. Can be prevented.

[Sixth Embodiment]
In order to prevent halation from occurring even when the reading optical axis 11 is displaced in the sub-scanning direction due to an assembly error or vibration, a halation line is formed in consideration of the amount of deviation of the reading optical axis 11 in the sub-scanning direction. It is preferable to specify.
As shown in FIG. 4, a reading area 12 is defined in the sub-scanning direction with the reading optical axis 11 interposed therebetween, and an inclination angle of the normal line of the original reading surface 18 with respect to the normal line of the original table 4 in the sub-scanning section is −ψ. Sometimes, the halation line LB is defined as a light path that propagates in the sub-scanning direction in the reading region 12 from the document surface end on the counter illumination mirror 10 side toward the light guide installation direction at an angle of −2 × ψ. preferable.
By defining in this way, even when the reading optical axis 11 is shifted to the position 11 ′, it is possible to avoid the occurrence of halation due to the illumination light from the counter illumination mirror 10 side.

[Seventh Embodiment]
As shown in FIG. 5, the entrance pupil diameter of the reading optical system 50 is r, the distance from the document reading surface 18 to the entrance pupil of the reading optical system 50 is D, and the angle determined from r and D is −ω = arc tan (r / D), if the angle formed by the specularly reflected light and the reading optical axis is smaller than −ω, the specularly reflected light does not enter the entrance pupil of the reading optical system 50, and therefore does not reach the image sensor, and halation. Does not occur.
In order to satisfy this, the halation line LA is defined as the position of the light beam whose light incident angle with respect to the reading center is 2ψ + ω, as shown in FIG. If the orientation control region 14 of the light guide 5 is located farther from the reading optical axis 11 in the sub-scanning direction than the halation line LA, any light beam reaching the reading center from the orientation control region 14 can be read by the document. Since the incident angle on the surface 18 becomes larger than 2ψ + ω, the incident angle does not enter the entrance pupil of the reading optical system 50 and no halation occurs.
In FIG. 5, in order to simplify the explanation, the light refraction at the original glass surface and the light guide interface is ignored, but it is desirable to consider these as well.

[Eighth Embodiment]
In order to prevent halation from occurring even if the reading optical axis 11 is deviated in the sub-scanning direction, the halation line LA of the seventh embodiment shown in FIG. Can be considered as the position of the light beam at which the incident angle of the light beam incident on is 2ψ + ω.
If the orientation control region 14 of the light guide 5 is located farther from the reading optical axis 11 in the sub-scanning direction than the halation line LA, any light beam that reaches the reading region 12 from the orientation control region 14 is read. Since the incident angle to the region 12 is larger than 2ψ + ω, the incident angle does not enter the entrance pupil of the reading optical system 20, and no halation occurs.

[Ninth Embodiment]
As shown in FIG. 6, the entrance pupil diameter of the reading optical system 50 is r, the distance from the original surface to the entrance pupil of the reading optical system is D, and the angle determined from r and D is ω = tan-1 (r / D). Then, if the angle formed by the specularly reflected light from the counter illumination mirror 10 and the reading optical axis 11 is larger than ω, the specularly reflected light does not enter the entrance pupil of the reading optical system 50, and therefore reaches the image sensor. Without the occurrence of halation.
In order to satisfy this, as shown in FIG. 6, the halation line LB may be considered as the position of a light beam whose light beam incident angle with respect to the reading center is − (2ψ + ω). If the counter illumination mirror 10 is arranged at a position farther from the reading optical axis 11 in the sub scanning direction than the halation line LB, any light beam that reaches the reading center from the counter illumination mirror 10 enters the reading surface 18. Since the angle is smaller than − (2ψ + ω), it does not enter the entrance pupil of the reading optical system 50, and no halation occurs.
In the explanatory diagram, in order to simplify the explanation, the light refraction on the surface of the original glass is ignored, but it is desirable to consider these as well.

[Tenth embodiment]
In order to prevent halation from occurring even if the reading optical axis 11 is deviated in the sub-scanning direction, the counter illumination mirror 10 is used not for the halation line LB of the ninth embodiment shown in FIG. It can be considered as the position of the light beam at which the incident angle of the light beam incident on the side end is − (2ψ + ω).
If the counter illumination mirror 10 is located farther from the reading optical axis 11 in the sub scanning direction than the halation line LB, any light beam that reaches the reading area 12 from the counter illumination mirror 10 enters the reading area 12. Since the angle is smaller than − (2ψ + ω), it does not enter the entrance pupil of the reading optical system 50 and no halation occurs.

[Eleventh embodiment]
In the original illumination unit of the present invention, it is preferable that the illumination light is diffused by the light guide 5 in the optical path from the light source 1 to the reading region 12.
For example, the light guide 5 can be configured to have a diffusion surface that diffuses illumination light.
By adopting such a configuration, it is possible to reduce component costs and assembly costs without increasing the number of diffusion members such as diffusion plates.
In addition, by diffusing the illumination light, the light energy density at which the glare emitted from the light source reaches the retina of the user who uses the device can be lowered, so that an illumination unit excellent in safety can be provided.
In the above-described conventional device, for example, in the device of Patent Document 1 shown in FIG. 11, a light beam emitted perpendicularly from the LED or a light beam group having a radiation angle close to this is reflected by the inclined surface 223e of the light guide plate, Since the light is reflected by the opposing mirror 225 and guided in the direction of the illumination area, it is inevitable that glare will occur when viewed directly from the illumination area side. Further, in the apparatus of Patent Document 2 shown in FIG. 12, a light beam emitted vertically from an LED or a light beam having a radiation angle close to that of the LED is reflected by the inclined surface of the light guide plate and directed toward the document surface. Since the light is emitted from the surface, it is inevitable that the light beam becomes glare when the output surface is directly viewed.

[Twelfth Embodiment: Document Reading Apparatus]
A document reading apparatus according to the present invention includes a document illumination unit according to the present invention, a reading optical system disposed on an optical path of reflected light from a document irradiated with illumination light from the document illumination unit, and a reading optical system. And an imaging device on which light is incident.
FIG. 8 shows a document reading apparatus according to the twelfth embodiment.
The document reading apparatus 20 includes a document illumination unit 21, a reading optical system including a first reflecting mirror 23, a second reflecting mirror 24, a third reflecting mirror 25, and an imaging element 27, and an image sensor ( CCD) 28.
The document illumination unit 21 includes an illumination optical system 21a and a counter illumination optical system 21b. The document illumination unit 21 illuminates the document 42 on the document table 4 in a line shape, and reflects the document reflected light by the reflecting mirrors 23, 24, and 25. The image of the original 42 is formed on the image sensor 28.

  The counter illumination optical system 21 b is the counter reflection member 10 that reflects the light beam emitted from the light guide 5. The first traveling body 22 including the document illumination unit 21 and the first reflecting mirror 23 is scanned at the scanning speed V, and the second traveling body 26 including the reflecting mirrors 24 and 25 is scanned at the scanning speed V / 2. Scan and scan the entire document surface.

The document reading device 20 of the present embodiment can be a thin device because the document illumination unit 21 of the present invention is significantly thin.
Further, by providing the document illumination unit 21 of the present invention, the orientation of illumination light can be controlled in both the main scanning direction and the sub-scanning direction, and the illuminance distribution characteristics can be controlled well even if the number of light source (LED) arrays is small. Therefore, it is possible to obtain an image signal having a high illuminance and strong against a reading position shift and high stability as a document reading apparatus.

[Thirteenth Embodiment: Document Reading Apparatus]
FIG. 9 shows a document reading apparatus according to the thirteenth embodiment.
In the document reading apparatus 30 according to the present embodiment, the document illumination unit 31, the reflection mirror 33, the imaging element 35, and the imaging element 36 are integrated in one housing 32. The reflection mirror 33 and the imaging element 35 constitute a reading optical system.
The traveling body 34 integrated by the housing 32 scans in the sub-scanning direction at the linear velocity V, and scans and reads the document 42.

The document reading device 30 of this embodiment has a simplified scanning mechanism and can be made thinner in the Y direction than the document reading device of the * embodiment shown in FIG.
Since the illumination device and the optical system are integrated, the error of the document reading position in the sub-scanning direction due to the dynamic vibration of the scanning drive is reduced, so that the fluctuation amount of the light intensity received by the image sensor is reduced. In view of the error, the illumination area necessary for reading need not be widened in the sub-scanning direction. It can also save energy.

[Fourteenth Embodiment: Image Forming Apparatus]
An image forming apparatus according to the present invention includes the document reading device according to the present invention and means for forming an image on a recording medium based on image information read by the document reading device.
FIG. 10 shows a schematic front view of the internal structure of a full-color copying machine as an example of an image forming apparatus according to the fourteenth embodiment.
An image forming unit 103 for forming a color image is provided at the center of the apparatus main body 102 of the copying machine 100. The image forming unit 103 includes four drum-shaped photosensitive members 104 that are spaced apart at equal intervals and arranged in parallel in the horizontal direction, a charging roller 105 that uniformly charges the outer peripheral surface of the photosensitive member 104, and a charging roller 105. An exposure device 106 that forms an electrostatic latent image by exposing the outer peripheral surface of each of the photosensitive members 104 charged in accordance with the image data, and supplying the toner to the electrostatic latent image to convert the electrostatic latent image into a toner image A developing device 107 that visualizes the toner image, an intermediate transfer belt 108 onto which the toner image on the photoconductor 104 is sequentially transferred, and a cleaning that removes toner remaining on the photoconductor 104 after the transfer of the toner image onto the intermediate transfer belt 108. The apparatus 109 includes a transfer roller 110 that transfers the toner image transferred onto the intermediate transfer belt 108 to the recording medium S, and the like.
Note that toner images of different colors (Y: yellow, M: magenta, C: cyan, K: black) are formed on the four photoconductors 104, and the toner images of these colors are formed on the intermediate transfer belt 108. By being transferred, a color toner image is formed on the intermediate transfer belt 108, and this color toner image is transferred to the recording medium S.

  On the upper part of the apparatus main body 102, an ADF 111 that automatically feeds a document that is an object to be illuminated by an illumination device described later, a contact glass 112 on which a document that is an illumination object by an illumination device to be described later is placed, and the ADF 111 automatically An image reading device 113 for reading the sent document or the document placed on the contact glass 112 is arranged.

  The image reading apparatus 113 according to the present invention includes first and second traveling bodies 114 and 115 capable of traveling at a speed of 2: 1 in parallel with the contact glass 112, a lens 116, a CCD 117 serving as an image reading unit, and the like. . The first traveling body 114 includes an illuminating device 118 for illuminating the document surface of the document placed on the contact glass 112 or the document conveyed by the ADF 111, and is reflected on the document surface and reflected on the reading optical axis. A first mirror 119 that reflects the reading light traveling along is mounted. A second mirror 120 and a third mirror 121 that further reflect the light reflected by the first mirror 119 are mounted on the second traveling body 115. A lens 116 and a CCD 117 are disposed in front of the reading light sequentially reflected by the first to third mirrors 119, 120, and 121 in the traveling direction.

  A plurality of, for example, four-stage paper cassettes 124 for storing the recording medium S are provided at the lower part of the apparatus main body 102. The recording media S stored in these paper cassettes 124 are separated and fed one by one by the pick-up roller 125 and the feed roller 126, and the separated and fed recording media S are conveyed by the paper provided in the apparatus main body 102. It is conveyed along the path 27. On the sheet conveyance path 127, a registration roller 128, a transfer roller 110, a fixing device 129, a paper discharge roller 130, and the like are arranged.

  In such a configuration, laser light corresponding to the image data of each color (yellow Y, magenta M, cyan C, black K) is emitted from the semiconductor laser of the exposure device 106 according to the reading result of the image reading device 113, An electrostatic latent image is formed by exposing the outer peripheral surface of each photoconductor 104 to which the laser light is uniformly charged by the charging roller 105. Each color toner is supplied from each developing device 107 to the electrostatic latent image, whereby a toner image of each color is formed. The toner image on each photoconductor 104 is sequentially transferred onto an intermediate transfer belt 108 that moves in synchronization with the photoconductor 104, and a color toner image is formed on the intermediate transfer belt 108.

On the other hand, when the image forming operation in the image forming unit 103 is started, the recording medium S starts to be separated and fed from the sheet cassette 124 and is separated and fed on the sheet conveyance path 127. Is transferred to a transfer position between the intermediate transfer belt 108 and the transfer roller 110 by a registration roller 128 that is driven to rotate intermittently.
Next, the registration roller 128 is rotationally driven, and the recording medium S is sent between the intermediate transfer belt 108 and the transfer roller 110, whereby the color toner image on the intermediate transfer belt 108 is transferred onto the recording medium S. The color toner image transferred onto the recording medium S is fixed to the recording medium S while the recording medium S passes through the fixing device 129, and the recording medium S on which the color toner image is fixed is discharged by the paper discharge roller 130. The paper is discharged onto the tray 131.
Note that the image reading apparatus 113 can be operated independently as a scanner apparatus.

  According to the image forming apparatus of the present invention, the image reading apparatus as the scanner unit can be made thinner and lighter than the conventional one, so that the material cost can be reduced. In addition, since the image forming apparatus of the present invention has high illumination efficiency and good illuminance flatness, the image signal is stable, the image quality is high, and the cost required for signal correction can be reduced. Furthermore, the energy density of the light emitted from the light source is low, and the safety for the user during work is excellent.

L (LA, LB) halation line 1 light source 2 light emitting surface 3 incident surface 4 document table 5 light guide 7 second exit surface 8 upper horizontal plane (first exit surface)
9 Lower horizontal plane 10 Opposing reflecting member (opposing mirror)
DESCRIPTION OF SYMBOLS 11 Reading optical axis 12 Reading area 13 Internal reflection area 14 Orientation control area 15 Orientation control surface 16, 17 Normal 18 Original surface 19 Reading optical axis side edge part of orientation control area 50 Reading optical system

JP 2010-252340 A JP 2010-191397 A

Claims (11)

In a document illumination unit in a document reading apparatus that irradiates light to a reading region of a document placed on a document table and reads reflected light from the document by an image reading element,
A plurality of light sources arranged in a line in the main scanning direction, an incident surface on which illumination light from the light source is incident, a first emission surface that irradiates the read illumination area with the incident illumination light, and the first emission A light guide having a second emission surface that irradiates in a direction different from the surface, and at least an opposing reflection member that guides the emitted light from the second emission surface of the light guide to the reading region,
The light guide is thin in the normal direction of the document table, and reflects the incident light from the light source on the inner surface facing the document table to propagate the light guide to the first surface. An internal reflection region that leads to the second exit surface, and an orientation control region that deflects the traveling angle of the light beam propagating inside the light guide to irradiate the reading region from the first exit surface,
For a first halation line that is a line of a light path from the reading area in the direction in which the light guide is installed, and an angle with respect to a normal line of the document table is a reference angle for occurrence of halation, The light guide is arranged so that the position in the sub-scanning direction of the reading region side end of the orientation control region is positioned farther from the optical axis of the reading region than the first halation line. Characteristic document illumination unit.   For a second halation line that is a ray path line from the reading area toward the direction in which the opposing reflecting member is installed, and an angle with respect to a normal line of the document table is a reference angle for occurrence of halation. The counter reflecting member is disposed such that the position of the end of the counter reflecting member on the side of the reading area in the sub-scanning direction is located farther from the optical axis of the reading area than the second halation line. The document illumination unit according to claim 1, wherein:   When the inclination angle of the normal line of the original reading surface with respect to the normal line of the original platen is ψ, the first halation line has an angle of 2 × ψ with respect to the normal line of the original platen. 3. The document illumination unit according to claim 1, wherein the document illumination unit is a line of a light beam path from a center in the sub-scanning direction toward a direction in which the light guide is installed.   When the inclination angle of the normal line of the original reading surface with respect to the normal line of the original platen is ψ, the first halation line has an angle of 2 × ψ with respect to the normal line of the original platen. 3. The document illumination unit according to claim 1, wherein the document illumination unit is a line of a light beam path from an end of the light guide to a direction in which the light guide is installed.   When the inclination angle of the normal line of the original reading surface with respect to the normal line of the original platen is −ψ, the second halation line has an angle of −2 × ψ with respect to the normal line of the original platen. 3. The document illumination unit according to claim 1, wherein the document illumination unit is a line of a light beam path from a center in a sub-scanning direction of a reading area to a direction in which the opposing reflection member is installed.   When the inclination angle of the normal line of the original reading surface with respect to the normal line of the original platen is −ψ, the second halation line has an angle of −2 × ψ with respect to the normal line of the original platen. 3. The document illumination unit according to claim 1, wherein the document illumination unit is a line of a light beam path from an end of the reading area on the side of the opposing reflection member toward a direction in which the opposing reflection member is installed.   7. The document illumination unit according to claim 1, wherein illumination light is diffused by the light guide in an optical path from the light source to the reading area.   The document illumination unit according to claim 7, wherein the light guide has a diffusion surface for diffusing illumination light. The document illumination unit according to any one of claims 1 to 8,
A reading optical system disposed on an optical path of reflected light from a document irradiated with illumination light from the document illumination unit;
An original reading apparatus comprising: an image pickup element on which light incident through the reading optical system is incident.   The document reading apparatus according to claim 9, wherein the document illumination unit, the reading optical system, and the image sensor are held in a single housing. The document reading device according to claim 9 or 10,
An image forming apparatus comprising: means for forming an image on a recording medium based on image information read by the document reading apparatus.

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