JP2000048616A - Light conductor, lighting system and image reader using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To set so that an incident light flux is properly emitted on a light conductor, to miniaturize the whole lighting system and to uniform the light quantity distribution by arranging a diaphragm for restricting a light flux emitted from the light incident surface. SOLUTION: A light flux from a light source 1 is emitted on the light conductor inside light source part 4, and only a light flux passing through the opening part of an aperture 2 being a light shielding body inserted into a light conductor F is emitted on the light conductive part 3. The light flux propagates in the lengthwise direction by being totally reflected by the light conductor side surface, and while being reflected or propagated by the saw-toothed light reflecting plate 5, the light flux reaches the light emitting part 6 at an incident angle smaller than a critical angle, and is emitted outside the light conductor F to illuminate the illuminating object surface in a line shape. Thus, the light flux from the light source 1 is restricted by the aperture 2, the light flux incident on the light conductive part 3 through the aperture 2 is emitted at an incident angle larger than a critical angle on the light conductor side surface, and the light flux is eliminated from being directly emitted from the light conductor end part to uniform the light quantity distribution of an illuminating light flux.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light guide, an illuminating device, and an image reading apparatus using the same, and more particularly to illuminating a document with a linear light beam while scanning the same, and transmitting the light beam from the document on a light receiving surface. To form an image of the original by reading the original and reading the original.

[0002]

2. Description of the Related Art FIG. 8 is a view for explaining a conventional example (Japanese Unexamined Patent Publication No. 9-61633), in which a light beam from a light source 27 is made to enter from an end of a columnar light guide 29 and the light inside the light guide 29 is formed. Is propagated, the light beam irradiated on the light diffusion unit 28 is diffused, and a part is emitted from the light emission unit 30 in the downward direction in the figure.

FIG. 9 is a diagram showing a light quantity distribution and an illumination principle obtained by the light guide 29 of FIG. Of the light beams incident on the light guide 29 from the light source 27, those incident on the inner wall of the light guide at an angle satisfying the total reflection condition are totally reflected and propagate in the light guide 29. Also, the light diffusing portion 28 of the light beam
Most of the light flux irradiated with the light strikes the light emitting portion 30 provided at a position facing the inner wall of the light guide at an angle that does not satisfy the condition for total reflection, and is emitted out of the light guide to become illumination light.

On the other hand, of the light beams from the light emitter 27, the light beams directly incident on the inner wall near the end of the light guide 29 at an angle that does not satisfy the condition for total reflection escape as it is from the light guide. Among the light beams from the light emitting body 27, the light beam irradiated on the light diffusion portion near the incident portion is also diffused, and then the light exits from the vicinity of the end portion to the outside of the light guide at an angle that does not satisfy the condition of total reflection. The light quantity distribution obtained in this manner becomes illumination light having a very high light quantity distribution in a portion near the incident surface as shown in FIG.

[0005]

That is, the conventional lighting device using the columnar light guide has the following problems.

[0006] A light beam incident from the end of the light guide is emitted out of the light guide without being totally reflected in the vicinity of the incident portion in the light guide, and a bright line-shaped peak is formed near the incident portion as shown in FIG. It will be a platform distribution that has. Also, the luminous flux that irradiates the diffusion part near the incident part also has a high light amount,
Since most of this light flux is emitted out of the light guide without being totally reflected, the illumination light amount distribution becomes extremely uneven in the vicinity of the incident portion. To avoid this, the irradiation light near the end of the light guide is not used, and if the entire length of the light guide is increased to cover the illumination range, the size of the lighting device is increased.

[0007] Three colors (RG
When the light emitting body of B) is arranged at the end of the light guide, the light amount distribution of the RGB light changes more sensitively due to the difference in the position of each light emitting body with respect to the light guide, which may cause a color shift in the read image. . In particular, at the end of the light guide, the light amount distribution for each RGB appears extremely due to the above phenomenon.

Therefore, in the present invention, a stop for restricting the incident light beam is provided, and the incident light beam is set so as to be appropriately incident on the light guide, so that the entire apparatus can be reduced in size and the light amount distribution can be made uniform. An object is to provide a light guide, a lighting device, and an image reading device using the same.

[0009]

The light guide, the illuminating device, and the image reading device of the present invention have the following configurations.

[1]: In a light guide having a columnar light-transmitting member, an end surface of which is a light incident surface, and at least a part of a side surface is a light exit surface, a light beam incident from the light incident surface is restricted. A light guide, comprising an aperture.

[2]: In a light guide having a columnar translucent member, an end face serving as a light incident surface, and at least a part of the side face being a light exit face, a light beam incident from the light incident face is directed to the side face. A light guide, comprising: a stop for restricting the light flux so as to be incident at an incident angle equal to or greater than the critical angle.

[3] The light guide according to [1] or [2], wherein the stop restricts the light flux in the direction of the light exit surface and in the side direction of the light guide facing the light exit surface. Light body.

[4]: The center of the aperture of the stop and the emission center of the light source of the light beam incident from the incident surface coincide with each other in the longitudinal direction of the light guide, the aperture width of the stop is d, and the distance between the light source and the stop is d. When the distance is L, the refractive index inside the light guide is n1, and the refractive index outside the light guide is n2, d ≦ 2Ltan (90−sin ⁻¹ (n2 / n1)). ], [2] or [3].

[5]: a surface of the stop on the light guide end side;
[1], [2], wherein at least a part of the side surface on the end side of the stop and the end surface is a mirror surface.
The light guide according to [3] or [4].

[6] The light guide according to any one of [5], wherein the mirror surface is shaped to reflect a light beam from a light source and pass through the stop.

[7] The light guide according to any one of [1] to [6], wherein the light incident surface and the stop are provided at both ends in the longitudinal direction.

[8]: any one of [1] to [6], wherein the light incident surface and the stop are at one end in the longitudinal direction, and the other end has an end reflection surface. A light guide according to the item.

[0018]

[9] The light guide according to any one of [1] to [8], wherein the light guide has a reflective portion on a surface facing the light exit surface.

[10]: The reflecting portion has a saw blade shape composed of a plurality of reflecting surfaces for reflecting a light beam from the light incident surface so as to be incident on the light emitting surface at an incident angle smaller than the critical angle. Feature

[9] The light guide according to the above.

[11]: The reflectance of the reflecting surface is 80%
The light guide according to [10].

[12]: A light beam from the light source is incident on the light incident surface of the light guide according to any one of [1] to [11], and is illuminated with the light beam emitted from the light exit surface. A lighting device for illuminating an object.

[13]: A light beam from a light source is made incident on an end surface which is a light incident surface of a columnar light guide, and an object to be illuminated is illuminated with a light beam emitted from a light exit surface provided on a side surface of the light guide. An illuminating device, comprising a diaphragm for restricting a light beam from the light source.

[14]: A light beam from a light source is made incident on an end surface which is a light incident surface of a columnar light guide, and an object to be illuminated is illuminated with a light beam emitted from a light exit surface provided on a side surface of the light guide. 2. An illumination device according to claim 1, further comprising a stop for restricting the light beam incident from the light incident surface such that the light beam enters the light guide side surface at an incident angle equal to or greater than the critical angle.

[15]: The center of the aperture of the stop and the emission center of the light source of the light beam incident from the incident surface coincide with each other in the longitudinal direction of the light guide, the aperture width of the stop is d, and the aperture width from the light source to the stop is When the distance is L, the refractive index inside the light guide is n1, and the refractive index outside the light guide is n2, d ≦ 2Ltan (90−sin ⁻¹ (n2 / n1)). ] Or [14].

[16]: A light source unit housing enclosing the light source is provided, the aperture is provided in a part of the light source unit housing, and the aperture and a part or all of the inner surface of the light source unit housing are provided. The lighting device according to [13], [14] or [15], which is a mirror surface.

[17]: The mirror surface on the inner surface of the light source unit housing is
A light beam from a light source is reflected so that the light beam passes through the stop and enters a light guide.
6] The lighting device according to the above.

[18] The lighting device according to any one of [10] to [17], wherein the light incident surface and the stop are provided at both ends in the longitudinal direction.

[19]: any one of [10] to [17], wherein the light incident surface and the stop are at one end in the longitudinal direction, and the other end has an end reflection surface. The lighting device according to any one of the preceding claims.

[20]: [10] to [1] characterized by having a reflecting portion on the surface facing the light exit surface.
9] The lighting device according to any one of the above items.

[21]: The reflecting portion has a saw blade shape composed of a plurality of reflecting surfaces for reflecting a light beam from the light incident surface so as to be incident on the light emitting surface at an incident angle smaller than the critical angle. The lighting device according to [20], wherein the lighting device is characterized in that:

[22]: The reflectance of the reflecting surface is 80%
The lighting device according to [21], wherein:

[23]: The light source is an LED arranged at a light incident position on the light incident surface.

The lighting device according to any one of [9] to [22].

[24] The lighting device according to [23], wherein the light source is a monochromatic LED.

[25] The lighting device according to [23], wherein the light source is an LED of a plurality of colors.

[26]: The light beam from the document illuminated by the illuminating means is made incident on the image forming lens, and the light beam from the image forming lens is guided onto the light receiving element surface, and the document is put on the light receiving element surface. An image reading apparatus for forming and reading an image of

[9] An image reading device comprising the lighting device according to any one of [25].

<Function> In the invention of the above [1], [2], [13] or [14], a stop for restricting incident light to the light guide is provided on the light incident surface at the end of the light guide. By this, the light flux from the light source is prevented from being emitted out of the light guide without being totally reflected in the light guide, and the high-luminance light flux emitted out of the light guide in the vicinity of the end of the light guide is restricted. It is possible to obtain a uniform light quantity distribution while reducing the size.

According to the invention [3], the aperture restricts the light incident on the light guide in the light guide irradiation direction and the reflection direction thereof, so that the luminous flux is limited only in the above-described direction. Since the light flux in the vertical direction is not limited, the light flux can be used effectively.

The invention according to the above [4] or [15], wherein the aperture is appropriately adjusted so that the light beam passing through the aperture of the aperture does not enter the side surface of the light guide at an incident angle smaller than the critical angle. With this setting, it is possible to prevent in advance the light flux which is not totally reflected and exits the light guide from entering the light guide, and a uniform light amount distribution can be obtained.

The above [5], [6], [16] or [1]
7] The invention according to 7), wherein at least a part of the surface of the stop on the light guide end side, the side surface on the end side of the stop, and the end surface is a mirror surface, so that the aperture of the stop is provided. The light beam that does not travel toward the aperture is reflected by the mirror surface and travels toward the aperture of the stop, so that the light beam can be used more effectively.

The invention of [7] or [18] is characterized in that the light incident surface and the stop are arranged at both ends of the light guide.
This allows a light beam to enter from both ends of the light guide, thereby obtaining a larger amount of emitted light. That is, brighter illumination can be obtained when the illumination device is configured.

The invention of [8] or [19] is characterized in that the light incident surface and the stop are arranged at one end of the light guide. Thus, when applied to a lighting device, the number of light sources is one, and a simpler configuration is possible.

The above

[9], [10], [20] or [2
According to the first aspect of the invention, since the reflecting section is provided on the side opposite to the light emitting section in the light guide, the light beam propagating in the light guide can be efficiently guided to the light emitting surface.

According to the invention [11] or [22], the reflectivity of the reflection surface provided on the opposing portion of the light exit portion in the light guide is 80%.
As described above, it is possible to efficiently guide the light beam propagating in the light guide to the light exit surface.

The invention of the above [12] is characterized by the following [1] to [1]
1) By using the light guide according to any one of the above items,
The distribution of the amount of illumination light is made uniform while the size of the device is reduced.

In the invention of the above [23] or [24], the light source is an LED, thereby enabling a compact and fine light amount adjustment.

In the invention according to the above [25], the light source is a multicolor L light source.
The use of the ED enables a lighting device capable of finely adjusting the amount of light.

According to the invention [26], the original is uniformly illuminated, and reading can be performed under better conditions.

[0048]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS <Embodiment 1> FIGS. 1, 2, 3 and 4 are views showing Embodiment 1 of the present invention, and FIG. 1 is a light guide which is a feature of this embodiment. FIG. 2 is a cross-sectional view of a short side (in a direction perpendicular to the longitudinal direction) of the light guide, and FIG. 3 is an explanatory view near an end which is a characteristic of the light guide. FIG. 4 is an explanatory diagram of an image reading device using the illumination device.

In FIG. 1, F is a light guide, 1 is a light source provided at an end of the light guide F, 2 is an aperture (aperture) for limiting a light beam from the light source 1, and 3 is the light guide. A portion for guiding the light beam passing through the stop 2 of F (light guide portion), 4 is a portion of the light guide F from the end where the light source 1 is arranged to the aperture 2 (light source portion), and 5 is a light guide length. A saw blade-shaped light reflecting portion 6 provided on a part of the side surface of the light guide along the hand direction is a light emitting portion provided on the side surface of the light guide facing the saw blade light reflecting portion 5.

First, a lighting device S using the light guide F of the present invention.
Will be described (FIGS. 1, 2, and 3).

A light beam from the light source 1 composed of LEDs of three colors of RGB enters from both ends of the light guide F. At this time, each light emitting body (LED) has a generally known wavelength. The light flux from the light source 1 is a light guide F
And only the light flux which is limited by the aperture 2 which is a light shield inserted in the light guide F and passes through the opening of the aperture 2 is incident on the light guide 3 (FIG. 3). The luminous flux propagates in the longitudinal direction, for example, by being totally reflected on the side surface of the light guide, and is reflected or propagated by the sawtooth-shaped light reflecting portion 5 and, at the incident angle smaller than the critical angle, while being propagated. And illuminates the surface to be illuminated linearly.

In this embodiment, the light beam from the light source 1 is restricted by the aperture 2, and the light beam incident on the light guide 3 through the aperture 2 is smaller than the critical angle with respect to the side surface of the light guide. The light is made incident at a large incident angle, and the light flux is not directly emitted from the end of the light guide, so that the light quantity distribution of the illumination light flux is made uniform.

Generally, the critical angle φ of the light beam incident on the light exit surface 6 is represented by φ = sin ⁻¹ (n2 / n1). (N
1: Refractive index inside the light guide, n2: Refractive index outside the light guide) That is, the included angle θ between the light beam incident on the light exit surface 6 and the end side surface is θ> 90−sin ⁻¹ (n2 / The light beam that satisfies n1) may be shielded by the aperture 2.

Accordingly, the center 2a of the aperture of the stop 2 and the center 1a of the light of the light source 1 coincide in the longitudinal direction of the light guide (in this example, coincident with the dashed line shown in FIG. 3), and the aperture width of the aperture 2 is reduced. d, when the distance between the light source and the aperture in the longitudinal direction of the light guide is L, by satisfying d ≦ 2Ltan (90−sin ⁻¹ (n2 / n1)), only the luminous flux that satisfies the condition of total reflection is apertured. 2 and a uniform light quantity distribution is obtained.

The light guide F has a columnar shape obtained by molding a resin, and its length in the longitudinal direction is long enough to illuminate the illuminated area. In addition, the area of the short cross section is the same at any position in the longitudinal direction, or is reduced as the distance from the light source is increased, so as to mitigate the inappropriateness of the light amount distribution in the longitudinal direction or to correct the decrease in the light amount at the end caused by the reading system. The shape to be performed. Further, when the cross-sectional area changes in the longitudinal direction, the case where the light emitting section 6 is parallel to the illuminated area and the case where the light emitting section 6 and the illuminated area are appropriately changed in order to perform more effective light amount distribution correction. The distance may be changed.

The light beam incident on the light guide of the light guide F propagates in the light guide. At the same time, a part of the light beam
%, And is reflected to the light emitting unit 6. The saw blade-shaped light reflecting portion 5 guides the light beam to the light emitting portion 6 by the saw blade-shaped reflecting surface 5a instead of simply diffusing and reflecting the incident light, so that the light beam is totally reflected efficiently. The light hits the inner wall of the light emitting section 6 at an angle closer to a right angle than a corner. As a result, the light beam is emitted with directivity from the light emitting section 6 having a light condensing effect on the short section of the light guide, and appropriately illuminates the surface to be illuminated.

The saw blade-shaped light reflecting portion 5 has a saw blade shape in the longitudinal section of the light guide F, and has a fine line shape formed with a narrow width along the longitudinal direction. The area of the sawtooth-shaped light reflecting portion 5 may be the same at any position in the longitudinal direction of the light guide F, or may be, for example, as the distance from the light source increases, in order to appropriately correct the irradiation light intensity distribution in the longitudinal direction. Is widened, and a light amount distribution as required is obtained. Further, reflecting surfaces 5 arranged along the longitudinal direction of the saw-shaped light reflecting portion 5
It is assumed that the pitch a is uniform at any position in the longitudinal direction, or is changed so as to more appropriately correct the irradiation light amount distribution in the longitudinal direction.

Next, an image input device (image reading device) using the above-described illumination device will be described (FIG. 4).

In FIG. 4, reference numeral 8 denotes a transparent original illuminated by the illuminating device S, 9 denotes an imaging lens for forming an image of the original 8, and 10 denotes a light receiving element (line sensor) for reading the image of the original 8. is there.

The light guide F of the illuminating device S and the transmissive original 8 are arranged close to each other.
Is directly illuminated, and the image information of the original 8 is imaged by the imaging lens 9 on the one-line sensor 10 as a reading unit at a predetermined magnification. At this time, it is assumed that the length of the light emitting portion 6 of the light guide F is equal to or longer than the reading width of the document 8, and the reading area of the document 8 is sufficiently illuminated. Then, the relative position with respect to the transparent original 8 is changed (the lighting device,
The image forming lens 6 and the line sensor 10 are moved (scanned) in the direction of the arrow in the drawing (in the sub-scanning direction), and the line sensor 10 reads the transparent original 8 as two-dimensional image information. The same operation is performed for each color. For example, the document is read by turning on only the R LED to read the document, and then turning on only G to read the document.

First, the light amount distribution correction in the longitudinal direction of the light guide is
The description is made by changing the cross-sectional area of the light guide 3, the pitch and width in the longitudinal direction of the saw-toothed light reflecting portion 5, the distance between the light emitting portion 6 and the irradiated surface, and the like. The light amount distribution to be corrected is made uniform according to the object to be illuminated, and the light amount distribution generated by the cosine fourth law of the imaging lens 9 in the image reading system as shown in FIG. and so on.

As described above, according to the present embodiment, the light source 1
Out of the light incident on the light guide F from the light guide F which is directly incident on the inner wall of the light guide at an angle that does not satisfy the condition of total reflection, is restricted by the aperture 2 in advance. The luminous flux incident on the light-guiding portion propagates through the light guide portion without being directly emitted, and is uniformly emitted in the longitudinal direction, so that illumination that is compact in the longitudinal direction and has little unevenness in the amount of light projected on the surface to be irradiated becomes possible.

Further, the image reading apparatus of the present embodiment has the effect that the speed of the apparatus can be increased and the image quality can be improved by providing a bright illuminating device without the above-mentioned unevenness in the light amount.

In particular, since the steep distribution of the illuminating light flux is reduced, even when a plurality of light-emitting elements (LEDs) are arranged, there is no color shift and high image quality when reading a color image can be achieved. This has the effect.

<Second Embodiment> FIG. 5 is a schematic view of a second embodiment according to the present invention. Since the basic configuration of this embodiment is almost the same as that of the first embodiment, the same elements are denoted by the same reference numerals and the description thereof will not be repeated.

In the present embodiment, the light source 1 disposed at the end of the light guide is included in the light source housing 14,
The light source is formed by providing an aperture 2 on the side of the light guide, and the light source is configured separately from the light guide F. Also, its housing 14
And the surface on the light source side of the aperture 2 are mirror surfaces.

As a result, of the light beams from the light source 1, the light beams restricted by the aperture 2 are reflected by the mirror surface, travel toward the aperture 2 again, pass through the aperture 2, as shown by the dotted line in FIG. The light amount can be added, and the steep light amount distribution can be further reduced.

The present embodiment is characterized in that the light source 1 is provided only on one end surface of the light guide F, and a light reflection surface (end reflection surface) 19 is provided on the opposite end.

As a result, the number of light sources can be reduced, and the cost can be reduced. Also, L
By arranging the light source 1 only on one side of the light guide F without reducing the number of EDs, it is possible to eliminate the LED at the opposite end and to configure a more compact lighting device.

<Third Embodiment> FIG. 7 is a schematic view of a third embodiment according to the present invention. Since the basic configuration of this embodiment is almost the same as that of the above-described second embodiment, the same components are denoted by the same reference numerals and the description thereof will not be repeated.

In the present embodiment, a reflecting surface (shape) that reflects a light beam from the light source 1, passes through the aperture, and enters the light guide F is reflected in the light source unit housing 14 containing the light source 1 and the aperture 2. (Mirror surface) 24 is provided.

As a result, of the light beams from the light source 1, the light beams restricted by the aperture 2 are reflected by the reflection surface 24.
Then, the light flux from the light source 1 can be effectively used while the sharp light amount distribution passing through the aperture 2 is further relaxed and further reduced.

[0073]

As described above, according to the present invention, a stop for restricting an incident light beam is provided, and the incident light beam is set so as to be appropriately incident on the light guide, thereby reducing the size of the entire apparatus. In addition, it is possible to provide a light guide, an illuminating device, and an image reading device using the same, which can make the light amount distribution uniform.

[Brief description of the drawings]

FIG. 1 shows a first embodiment.

FIG. 2 is a diagram showing a first embodiment.

FIG. 3 is a diagram showing a first embodiment.

FIG. 4 is a diagram showing an example of application of the device of the first embodiment.

FIG. 5 is a diagram showing a second embodiment.

FIG. 6 is a diagram showing the effect of the second embodiment.

FIG. 7 shows a third embodiment.

FIG. 8 shows a conventional example.

FIG. 9 shows a conventional example.

[Explanation of symbols]

 1: Light source 2: Aperture 3: Light guide 4: Light source in light guide 5: Saw blade-shaped light reflector 6: Light exit 8: Transmission original 9: Imaging lens 10: Light receiving element 11: Light source 19: Light guide Light body end reflection surface 27: Light source part 28: Diffusion part 29: Light guide 30: Light emitting part F: Light guide S: Lighting device

Claims (26)

[Claims] 1. A light guide, which is a columnar translucent member, has an end surface as a light incident surface, and at least a part of a side surface as a light exit surface, wherein a stop for restricting a light beam incident from the light incident surface is provided. A light guide characterized by being provided. 2. A light guide, which is a columnar translucent member, having an end face as a light incident surface and at least a part of a side surface as a light exit surface, wherein a light beam incident from the light incident surface is critical to the side surface. A light guide provided with a stop for restricting the light flux so as to be incident at an angle of incidence greater than or equal to an angle. 3. The light guide according to claim 1, wherein the stop restricts a light beam in a direction of the light exit surface and in a side direction of the light guide facing the light exit surface. 4. The center of the aperture of the stop and the emission center of the light source of the light beam entering from the incident surface coincide with each other in the longitudinal direction of the light guide, the opening width of the stop is d, and the distance from the light source to the stop is d. L, the refractive index inside the light guide is n1, and the refractive index outside the light guide is n
The light guide according to claim 1, wherein d ≦ 2Ltan (90−sin ⁻¹ (n2 / n1)), where 2. 5. The optical system according to claim 1, wherein at least a part of a surface of the stop on the light guide end side, a side surface on an end side of the stop, and an end surface is a mirror surface. 2,3 or 4
The light guide as described. 6. The light guide according to claim 5, wherein the mirror surface is shaped to reflect a light beam from a light source and pass through the stop. 7. The light guide according to claim 1, wherein the light incident surface and the stop are provided at both ends in a longitudinal direction. 8. The apparatus according to claim 1, wherein the light incident surface and the stop are located at one end in the longitudinal direction, and the other end is provided with an end reflecting surface. Light guide. 9. The light guide according to claim 1, further comprising a reflection portion on a surface facing the light exit surface. 10. The reflection part has a saw blade shape including a plurality of reflection surfaces that reflect a light beam from the light incident surface so as to be incident on a light exit surface at an incident angle smaller than a critical angle. The light guide according to claim 9, wherein: 11. The light guide according to claim 10, wherein the reflectance of the reflection surface is 80% or more. 12. A light beam from a light source according to claim 1,
Light incident on the light incident surface of the light guide according to any one of 1;
An illumination device, wherein an object to be illuminated is illuminated with a light beam emitted from the light exit surface. 13. An illuminating device for illuminating an object to be illuminated with a luminous flux from a light source incident on an end face, which is a light incident surface of a columnar light guide, and radiating from a light exit surface provided on a side surface of the light guide. 2. The lighting device according to claim 1, further comprising a stop for restricting a light beam from the light source. 14. An illuminating device for illuminating an object to be illuminated with a luminous flux from a light source incident on an end surface, which is a light incident surface of a columnar light guide, and radiating from a light exit surface provided on a side surface of the light guide. 3. The illumination device according to claim 1, further comprising a stop for restricting the light flux so that the light flux incident from the light incident surface is incident on the side surface of the light guide at an incident angle equal to or greater than the critical angle. 15. The center of the aperture of the stop and the emission center of the light source coincide in the longitudinal direction of the light guide, the opening width of the stop is d, the distance from the light source to the stop is L, The lighting device according to claim 13, wherein d ≦ 2Ltan (90−sin ⁻¹ (n2 / n1)), where n1 is a refractive index and n2 is a refractive index outside the light guide. 16. A light source unit housing enclosing the light source, wherein the aperture is provided in a part of the light source unit housing, and a part or all of the aperture and the inner surface of the light source unit housing are mirror surfaces. The lighting device according to claim 13, wherein the lighting device is provided. 17. The light source unit according to claim 16, wherein a mirror surface on an inner surface of the light source unit casing has a shape in which a light beam from the light source is reflected to pass through the stop and enter a light guide.
The lighting device according to claim 1. 18. The apparatus according to claim 10, wherein the light incident surface and the stop are provided at both ends in the longitudinal direction.
The lighting device according to claim 1. 19. The apparatus according to claim 10, wherein the light incident surface and the stop are located at one end in the longitudinal direction, and the other end is provided with an end reflecting surface. Lighting equipment. 20. The lighting device according to claim 10, further comprising a reflection portion on a surface facing the light exit surface. 21. The light emitting device according to claim 21, wherein the reflecting portion has a saw blade shape including a plurality of reflecting surfaces for reflecting the light beam from the light incident surface so as to be incident on the light emitting surface at an incident angle smaller than the critical angle. The lighting device according to claim 20, wherein 22. The lighting device according to claim 21, wherein the reflectance of the reflection surface is 80% or more. 23. The lighting device according to claim 9, wherein the light source is an LED arranged at a light incident position on the light incident surface. 24. The lighting device according to claim 23, wherein the light source is a monochromatic LED. 25. The lighting device according to claim 23, wherein the light source is an LED of a plurality of colors. 26. A light beam from a document illuminated by an illuminating means is incident on an image forming lens, and the light beam from the image forming lens is guided onto a light receiving element surface, and an image of the document is formed on the light receiving element surface. 26. An image reading apparatus for performing reading by forming an image, comprising: the lighting device according to claim 9 as said lighting means.