JP2008270885A - Lighting device and document reader using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lighting device having high efficiency by reducing loss of a light quantity, providing uniform and stable light irradiation and having a deep light quantity depth. <P>SOLUTION: The lighting device is equipped with a light guide body 1 made of a transparent material and light sources provided at both ends of the light guide body, and the light guide body has an optical area provided on a surface in a length direction; a light exit portion R3 configured such that light emitted from a light source is made incident into the light guide body and light having passed through the optical area is emitted from a surface on one side in the length direction facing the optical area of the light guide; and a tapered portion R2 which is connected to the light exit portion and light sources and forms a tapered surface such that an external surface gradually expands from the light source to the light exit portion. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an illumination device and a document reading device using the illumination device, and more particularly to an illumination device using a light guide.

  In general, a facsimile reader, an image reader, or the like uses a document reading device including a contact image sensor that reads a document surface as image information.

  As shown in a cross-sectional view of an example in FIG. 8, the document reading apparatus irradiates the document 101 through the platen 100, and a platen 100 made of a light-transmitting glass plate for closely reading and reading the document 101. Light sources 104a and 104b, a rod lens array 200 that receives reflected light (secondary reflected light) from the document surface, and a light receiving element 201.

  Next, the operating principle of this document reading apparatus will be described. The light emitted from the light sources 104 a and 104 b is applied to the document placed on the platen 100. Therefore, the reflected light corresponding to the density and color of the original passes through the rod lens array 200 and forms an image on the light receiving element 201. In the light receiving element 201, the optical signal is converted into an electric signal, amplified, and finally output as a sensor output signal.

  Conventionally, a xenon lamp (Xe) is used as a light source of an original reading apparatus. However, the xenon lamp requires an inverter circuit for driving, and has a problem that it is expensive as a system constituting the light source.

Thus, an LED array is used in which a plurality of LED chips are linearly arranged at predetermined intervals on a substrate on which circuit conductors are formed.
However, in the LED array as described above, due to the directivity characteristics of the LED chip, the illumination efficiency is low and the variation in the illuminance on the document surface is large, which has been a cause of reducing the image reading performance. Further, it is necessary to provide a certain distance from the document surface to the LED array, the size of the unit itself becomes large, and the use of a large number of LED chips has caused a cost increase.

  Therefore, the present applicant uses a light guide, makes light incident from the end (both ends or one end) surface thereof, and uses a large number of triangular wave-shaped light refraction areas and / or reflection areas provided on one side surface of the light guide. A linear illumination device has been proposed that is refracted or reflected and emitted linearly (Patent Document 1). As a result, there is no need to worry about variations in illuminance on the document surface, the distance from the linear illumination device to the document surface can be shortened, light transmission efficiency can be dramatically improved, and an LED as a light source can be used. The number of chips can be drastically reduced and the cost can be reduced.

  As shown in FIG. 27, this linear illumination device is made of a light-transmitting material and has a longitudinal direction of a light guide 301 configured such that the cross-sectional area (diameter of the circle) decreases from both ends toward the center. A light refracting / reflecting region comprising a large number of triangular wave prisms 302 is provided on one surface, and light from the LED chip 304 provided at the end of the light guide 301 is propagated through the light guide 301. The light is emitted by the prism 302 and irradiated on a line along the longitudinal direction of the light guide 301. Here, the LED chip 304 as a light source is mounted on a circuit board 303 provided at an end of the light guide 301, and light is incident on the light guide 301 by a concave reflection surface 305 formed on the surface of the circuit board 303. Thus, the light guide 301 is led through the connection portion 306. The connection portion 306 is formed in a cylindrical shape, and a light diffusion layer 307 is provided on the outer periphery thereof, and is a connection portion that guides light from the LED chip 304 to the light guide 301.

  With this configuration, the light component that reaches the side surface of the connection portion 306 out of the light incident on the connection portion 306 is diffused by the light diffusion layer 307, and most of the light component can enter the light guide 301. Yes. The light component incident on the light guide 301 is emitted directly from the side surface of the light guide 301 or reaches the prism 302 constituting the light refraction / reflection region while repeating total reflection several times on the side surface. The angle is suddenly bent (that is, angle conversion is performed), and the light is emitted upward from the light guide 301 to illuminate the document.

  By this light diffusion layer 307, light is not emitted directly from the side surface of the connection portion 306, but is repeatedly reflected in the connection portion 306 and guided to the light guide 301. Since the light is emitted in the reflection region, the illuminance on the document surface can be made uniform.

  However, the diffusion of light at this connection portion 306 causes components of light in all directions, resulting in a large loss of light. There is a limit to the amount of light that can be obtained at the center of the light guide, that is, the portion far from the LED. there were.

In addition, as shown in FIG. 28, a light guide body is also proposed in which a light emitting portion is configured directly from a light source including an LED chip 304 without providing a connection portion.
In this case, much of the direct light will be emitted in the vicinity of the light source, and the amount of light is large at both ends of the light guide, but sufficient light cannot be obtained at the center of the light guide. was there.

JP-A-10-150526

In recent years, there has been an increasing demand for higher image quality in document reading devices, and there is a need for an illumination device that can reduce light loss and supply more uniform and stable light to the document surface. .
The present invention has been made in view of the above circumstances, and an object of the present invention is to reduce the loss of light amount and realize a highly efficient lighting device.
It is another object of the present invention to provide an illumination device that can perform uniform and stable light irradiation.
Another object of the present invention is to provide an illumination device with a high light intensity depth.

Therefore, the illumination device of the present invention guides the light emitted from the light source and the light source, further converts the angle of the light, emits the light to the outside, and the light from the light source. An optical path portion having a cross-sectional area larger than the light source side than the light source side is provided between the light source and the light guide so as to be guided to the light guide.
According to this configuration, light from the light source can be guided as far forward as possible (longitudinal direction of the light guide), and most of the light can be taken into the light guide, thereby improving efficiency and obtaining high illuminance. Can do. For example, even when light from a light source disposed on the side surface is emitted as parallel light from the front, it is possible to obtain uniform light with high efficiency.

Moreover, this invention is an illuminating device provided with the light guide which consists of a translucent material, and the light source provided in the both ends of the said light guide, Comprising: The said light guide is provided in the surface of a longitudinal direction And the light emitted from the light source is incident on the inside of the light guide, and the light passing through the optical region is one side surface in the longitudinal direction facing the optical region of the light guide A light emitting part configured to be emitted to the outside from the light source, the light emitting part, and a tapered part connected to the light source and forming a tapered surface whose outer surface gradually spreads from the light source toward the light emitting part; It is characterized by comprising.
With this configuration, since the light from the light source can be guided forward as much as possible by the tapered portion and most of the light can be taken into the light guide, efficiency can be improved and high illuminance can be obtained.

Moreover, this invention includes the said illuminating device in which the said taper part is a conical surface.
With this configuration, a gentle tapered surface can be obtained in the circumferential direction, and light from the light source can be more efficiently guided to the light emitting portion.

In the illumination device according to the aspect of the invention, the taper portion may include a taper angle that allows light from the center of the light source to enter the optical region of the light emission portion at an obtuse angle.
With this configuration, light can be taken into the light emitting device.

Moreover, this invention includes the said illuminating device in which the said taper part is a taper part with a discontinuous part.
With this configuration, by optimizing the shape of the tapered part with discontinuous parts, the light from the light source can be guided as far forward as possible, and most of the light can be taken into the light guide, thus improving efficiency. High illuminance can be obtained.

Moreover, this invention includes the said illuminating device in which the said taper part is integrally formed with the said light-projection part.
With this configuration, there is no attenuation of light at the connection portion, and high efficiency can be achieved with a simpler shape.

Moreover, this invention includes the said illuminating device in which the outer surface of the said taper part comprised the reflective surface.
With this configuration, it is possible to efficiently capture light.

Moreover, this invention includes the said illuminating device in which the length of the said taper part is 5.5 to 6.5 mm.
With this configuration, higher efficiency can be achieved. From the experimental results, it was possible to obtain higher brightness when the length of the tapered portion was 5.5 to 6.5 mm.

Moreover, this invention WHEREIN: The said light guide includes the thing in which the cross section perpendicular | vertical to a longitudinal direction is elliptical in the said light-projection part in the said illuminating device.
With this configuration, it is possible to obtain parallel light by once condensing at the focal point of the ellipse and taking it out from here.

In the illumination device according to the aspect of the invention, the light guide may have a cross section perpendicular to the longitudinal direction having an elliptical shape on the light emission surface side of the light emission portion, and the surface side facing the light emission surface. Then, including what is a circle.
With this configuration, light can be extracted to the front more efficiently.

Further, the present invention provides the above lighting device, wherein the light guide is in the light emitting unit,
Including the optical region being the focal point of the ellipse.
With this configuration, parallel light can be emitted efficiently.

Moreover, this invention includes the said illuminating device in which the said optical area | region is a reflective surface.
With this configuration, it is possible to reflect light in the optical region and efficiently extract light to the front surface.

Further, the present invention includes the illumination device, wherein the optical region is a surface having a high refractive index.
With this configuration, it is possible to efficiently realize light confinement in the optical region.

Moreover, this invention includes the said illuminating device with the said optical area | region provided with the slit which comprises a prism.
With this configuration, light can be emitted by causing reflection on the surface of the prism.

Further, the present invention includes the illumination device, wherein the light emitting portion is configured such that the outer diameter decreases toward the center.
With this configuration, it is possible to realize more uniform light irradiation by confining light.

Further, the present invention includes the above-described illumination device, wherein the slit is configured such that a width in a direction perpendicular to a longitudinal direction of the light guide becomes smaller toward the center.
Conventionally, when the light cannot be sufficiently confined, it is necessary to enlarge the slit toward the center and emit as much light as possible, but in this case, the peak width is reduced. Therefore, the slit width can be reduced toward the center of the light guide, the peak width can be increased, and the depth of light can be improved.

Moreover, this invention includes the said illuminating device in which all the shapes of the cut surface parallel to the both end surfaces of the said light guide are similar in all the cut surfaces.
With this configuration,

Further, the present invention includes the above illumination device in which the longitudinal direction in which the light from the light emitting portion is emitted is a surface perpendicular to both end surfaces.
With this configuration,

Further, the present invention includes the illumination device, wherein the light source is a light emitting diode.
This configuration is less expensive than using a xenon lamp.

Further, the present invention includes the illumination device, wherein the light emitting diode is mounted on a concave reflecting surface formed on a circuit board.
With this configuration, light can be extracted more efficiently.

  In the illumination device according to the present invention, the concave reflection surface may have an inverted truncated cone shape, and the light emitting diode may be mounted on the bottom surface of the inverted truncated cone shape.

Further, the present invention includes the above lighting device, wherein the light emitting diode is connected to the light guide so as to optically match with a transparent resin having the same refractive index as the light guide.
With this configuration, it is possible to extract light more efficiently without attenuation.

Moreover, this invention includes the said illuminating device in which the said light source is an electroluminescent element.
With this configuration, the cost can be reduced.

Further, the present invention includes the light guide that includes an angle conversion unit and is formed so as to emit two-dimensional light.
With this configuration, it is possible to provide a degree of freedom in design, and it is possible to obtain more uniform light.

In addition, the present invention includes the above-described illumination device disposed as a light source for irradiating a document, an optical system that transmits reflected light from the surface of the document, and a light receiving element that receives the reflected light through the optical system. An original reading apparatus is provided.
A small, uniform and high-luminance irradiation surface can be obtained, and an inexpensive document reading apparatus can be provided.

According to the illumination device of the present invention, the end portion of the light guide has a tapered portion that forms a tapered surface whose outer surface gradually spreads from the light source toward the light emitting portion. Light loss can be reduced and guided to the inside of the light guide, light loss at the end of the light guide can be reduced, and a highly efficient lighting device can be provided.
Moreover, according to the illuminating device of this invention, a uniform and stable linear illuminating device can be provided.

(Embodiment 1)
Hereinafter, the linear illumination device according to the first embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a configuration diagram showing the configuration of the linear illumination device according to Embodiment 1 of the present invention. FIG. 1 (a) is a side view of the linear illumination device, and FIG. 1 (b) and FIG. 1 (c). ) Are a front AA ′ cross-sectional view and an enlarged explanatory view of a main part in FIG. FIG. 2 is an enlarged view of a side sectional view (a) of the linear illumination device in FIG. 1, and shows the light path by arrows b1, b2, and the like. FIG. 3 is an explanatory view of the main part shape of the linear illumination device. 4 and 5 are diagrams showing the optical region 2 side of the linear illumination device of the present embodiment and a diagram showing the illuminance distribution.

  This linear illumination device is equipped with a light guide 1 made of translucent acrylic resin and LED chips 4 (not shown in FIGS. 1 and 2) provided at both ends of the light guide 1. An optical region 2 comprising a reflecting surface having slits S (see FIG. 2) provided at predetermined intervals on the surface in the longitudinal direction, and a light source. The light emitted from the portion R1 is incident on the inside of the light guide 1, and the light that has passed through the optical region 2 is emitted to the outside from one longitudinal surface facing the optical region 2. A light emitting portion R3, and a tapered portion R2 connected to the light emitting portion R3 and the light source portion R1 and constituting a tapered surface whose outer surface gradually spreads from the light source portion R1 toward the light emitting portion R3 are provided. It is characterized by that. The outer surface of the tapered portion R2 constitutes a reflective layer 7 made of, for example, an aluminum layer formed by electroforming. The light incident from the light source part R1 is reflected by the reflective layer of the taper part R2, and is incident at an obtuse angle on one surface of the prism formed by the slit S provided on the reflective surface of the light emitting part R3. And it is comprised so that it may radiate | emit to the light-projection surface side. That is, when the light incident from the narrowed side of the taper portion R2 is guided in the direction in which the taper portion R2 spreads, the light is reflected along the longitudinal direction of the light guide 1 every time the light is repeatedly reflected by the reflection surface 7. An angle conversion is performed in the direction (that is, to approach parallel to the longitudinal direction of the light guide 1).

  As shown in the AA cross section of FIG. 1B, the light emitting portion R2 has an elliptical cross section perpendicular to the longitudinal direction of the light guide 1 on the light emitting surface side D2 of the light emitting portion R3. At the same time, the surface side opposite to the light exit surface, that is, the side D1 of the optical region 2 forms a circle, and the slit S is a prism formed by the slit S provided at a position corresponding to the focal position of this ellipse. Is reflected as light in a state close to parallel light from the light emission surface side D2 of the light guide plate. FIG. 2 shows the behavior of light from the light source unit R1 in the light guide 1 by arrows. As is apparent from FIG. 2, the light from the light source R1 is subjected to angle conversion by the taper R2 before being guided to the light guide 1, and light having a uniform light quantity distribution is emitted to the light exit surface D2 side. The

  In addition, as shown in FIG. 3, the LED chip 4 is mounted on the surface of the circuit board 3 via an insulating layer (not shown), and the LED chip 4 has a concave reflecting surface 5 around the LED chip 4. Light is efficiently emitted toward the tapered portion R2 of the light guide 1.

This linear illumination device will be described more specifically.
The light source part R1 is formed as follows. First, an insulating layer is formed by applying an organic film having a thickness of about 100 μm on the surface of an Al substrate having a thickness of 0.6 to 2.0 mm, and a copper foil (thickness of 35 to 70 μm) is pasted thereon and etched. Then, a circuit pattern is formed by patterning and gold (Au) is formed thereon by electrolytic (or electroless) plating to form a circuit board 3.

  Next, the concave reflecting surface 5 is formed on the surface of the circuit board 3 by a stamping method using a mold. The shape of the concave reflecting surface is preferably an inverted frustoconical shape, and by using the inverted frustoconical shape, light from the LED chip 4 can be efficiently emitted forward and with a necessary angular distribution.

  Thereafter, the LED chip 4 is mounted on the circuit board 3 on the bottom surface of the inverted frustoconical shape of the concave reflecting surface 5 by using a die mounter. As the LED chip 4 used here, GaP is used for monochrome image reading, and a green bare chip such as a quaternary system such as AlGaInP is used when a high luminance one is required. In the case of a linear illumination device for reading color images, LED chips of three colors R (red), G (green), and B (blue) may be mounted side by side. In this way, the light source part R1 is produced. By simultaneously emitting light of these three colors of RGB, it can be used as a white light source and reflected light of the original illuminated by the light emitted from the linear illumination device (more correctly, secondary reflection scattered by the original surface) The original can be read by detecting the light) with an image sensor in which, for example, R, G, and B color filters are configured in the longitudinal direction (main scanning direction).

  Next, regarding the light guide 1, that is, the tapered portion R2 and the light emitting portion R3, and the many slits S having a triangular cross-section constituting the optical region 2 that performs light refraction / reflection are provided therethrough. It is integrally formed by injection molding with an acrylic resin which is a light resin. A large number of slits S constituting the optical region 2 that performs light refraction / reflection are formed on one surface of the light guide 1. Here, as the translucent resin material, in consideration of translucency, heat resistance, and resin flow at the time of injection molding, in addition to heat-resistant acrylic, polycarbonate, amorphous polyolefin, or the like can be applied.

  Further, an aluminum layer is formed on the outer surface of the taper portion R2 by electroforming to constitute the reflecting surface 7. The reflective surface may be configured by attaching a sheet having a mirror surface, for example.

Finally, the light source unit R1 and the light guide 1 are connected via a translucent resin having the same refractive index (about 1.5) as the light guide material. As the light-transmitting resin, an epoxy-based or modified acrylate-based UV curable resin is used.
In the first embodiment, the light guide 1 having a complicated shape as described above is integrally formed by injection molding. For example, the tapered portion R2 and the light emitting portion R3 are formed separately, The light guide body 1 may be manufactured by directly bonding or bonding using an adhesive, and the light source section R1 may be further bonded to the light guide body 1.

  The operation principle and characteristics of the linear illumination device according to the first embodiment formed as described above will be described with reference to FIG. FIG. 2 is an enlarged view of a side sectional view (a) of the linear illumination device in FIG. 1, and shows the path of light by arrows b1, b2, and the like. FIG. 3 is an explanatory view of the main part shape of the linear illumination device.

First, of the light emitted from the LED chip 4, a part of the light component emitted forward is directly incident on the tapered portion R2, and the light component emitted in the lateral direction is reflected by the concave reflecting surface 5 to be tapered. Incident to R2. Here, the taper angle of the concave reflecting surface 5 is adjusted, and the light is condensed at the center point O at the end of the tapered portion R2 on the light source side, and adjusted so as to be emitted from this center point. From this center point O, the light component b1 emitted forward is directly incident on the light emitting part R3 of the light guide, and the light component b2 emitted laterally is reflected by the taper part R2 and incident on the light emitting part R3. To do. Of the light components incident on the light emitting portion R3, the light component b1 incident on the direct light emitting portion R3 is optically constituting a photorefractive / reflective surface while repeating total reflection on the side surface of the light emitting portion R3. The angle is rapidly bent by reaching the region 2 and being reflected by the prism surface formed by the slit S. This prism surface is configured to include an elliptical focal position that forms the outer surface of the light guide 1 on the side of the document surface (for example, the central portion of the prism surface may be configured to coincide with the focal position). The light emitted from the prism surface is emitted, for example, as a light component b3, and irradiates the document surface arranged in front of the arrow. The diameters r1, r2, and r2 of the inverted truncated cone constituting the tapered portion so that almost all the light components directly incident on the light guide 1 from the tapered portion R2 are totally reflected by the side surface of the light emitting portion R3 of the light guide 1. The dimensions of the length L of the tapered portion and the refractive index n _LG of the light guide 1 are determined (see FIG. 10. In FIG. 10, r1 = 3.2 mm, r2 = 4.5 mm, and L = 6 mm are set. Have been).

  Of the light incident on the tapered portion R2, the light component b2 reaching the side surface of the tapered portion R2 can be almost entirely incident on the light emitting portion R3 by total reflection (or specular reflection). The light component b2 incident on the light emitting portion R3 is emitted directly from the side surface of the light emitting portion R3 or reaches the optical region 2 while repeating total reflection on the side surface several times. The original is illuminated as the light component b3 from the light emitting portion R3 that is reflected and constitutes the light guide 1.

Next, a configuration for uniformly emitting the light component b3 on the line will be described. 4 and 5 are diagrams showing the optical region 2 of the linear illumination device of the present embodiment and the illuminance distribution thereof.
In the present embodiment, the slits S are formed at a predetermined interval d in the light emitting portion R3 configured such that the outer diameter decreases toward the center, but the interval d decreases as the distance from the center increases. The slit S is configured such that the width W in the direction perpendicular to the longitudinal direction of the light guide 1 decreases as the distance from the central portion in the longitudinal direction of the light guide 1 decreases. In addition, the shape of the cut surface parallel to the both end surfaces of the light guide 1 is similar in all cut surfaces.

In this manner, the light from the light source part R1 is guided as far as possible (longitudinal direction of the light guide 1) by the taper part R2, and this is totally reflected by the prism formed by the slit S. However, since most of the light can be efficiently guided forward by the taper portion R2, the slit width W can be reduced in the vicinity of the center portion. A sufficient amount of light can be emitted. The illuminance distribution in the sub-scanning direction (direction perpendicular to the longitudinal direction of the light guide) is shown in FIGS. FIG. 5B shows the illuminance distribution in the central portion of the light guide 1 in the longitudinal direction (main scanning direction), which has a width in the vicinity of the peak. On the other hand, FIG. 6B shows the illuminance distribution at the end of the light guide 1, which is a distribution having the same width as the central portion in the vicinity of the peak.
This is obtained by adjusting the slit width W, and the flat area is too large in the illuminance distribution in the sub-scanning direction as in the conventional case where the slit width W is increased at the center. As a result, a sufficient depth of light quantity can be obtained without unnecessarily increasing the total light quantity.
On the other hand, in order to eliminate the non-uniformity of the light amount distribution at the end portion and the center portion in the longitudinal direction of the light guide 1, the slit width W is made larger at the end portion than at the center portion. This also slightly increases the slit width W as compared with the prior art. As shown in FIG. 27, this corresponds to a reverse configuration in which the slit width W is increased at the center and decreased at the end.
By adjusting the slit width in this way, an ideal illuminance distribution can be obtained in both the sub-scanning direction and the main scanning direction.

Based on this principle of operation, an original reading apparatus using an A4 size linear illumination device for a scanner as shown in FIG. 7 and an explanatory cross-sectional view in FIG. 8 was manufactured and its characteristics were evaluated.
As shown in a sectional view of an example in FIG. 8, the document reading apparatus has a platen 100 made of a light-transmitting glass plate for closely contacting and reading the document 101, and the document 101 via the platen 100. Light sources 104a and 104b, a rod lens array 200 that receives reflected light from the document surface, and a light receiving element 201.

  Next, the operating principle of this document reading apparatus will be described. The light emitted from the light sources 104 a and 104 b is applied to the document placed on the platen 100. Therefore, the reflected light corresponding to the density and color of the original passes through the rod lens array 200 and forms an image on the light receiving element 201. In the light receiving element 201, the optical signal is converted into an electric signal, amplified, and finally output as a sensor output signal.

  As a result, when four LED elements (GaP, λ = 565 nm) are used as the light sources 104a and 104b, an original surface illuminance of 8,000 lx and an illuminance variation of ± 10% or less are realized. Compared with a conventional LED array in which a plurality of LEDs are arranged in the main scanning direction, the number of LED elements can be reduced to about 1/10, and the distance from the illumination device to the document surface is the case of the conventional LED array. Although about 8 to 10 mm was necessary, the main line illumination device was able to sufficiently suppress the illuminance variation even when approaching 1.5 mm. As a result, the maintenance is easy and the cost can be reduced.

  In addition, a red LED (GaAlAs) element, a pure green LED (GaN) element, and a blue LED (GaN) element are mounted one by one, and light source switching type color image reading device is turned on sequentially from red → green → blue. It is also possible to realize a linear illumination device for use.

(Embodiment 2)
In the first embodiment, the slit S is formed so as to be accommodated in the circular portion constituting the lower portion of the light emitting portion R3. However, as shown in FIG. 9 (and FIG. 10), the slit S protrudes from the circular portion of the light emitting portion R3. You may form so that it may do.

Next, Example 1 of the present invention will be described.
In the first embodiment, a linear illumination device will be described.
The linear illumination device of Example 1 has the structure shown in FIGS. 1 to 4 in Embodiment 1, and as shown in FIG. 10, the shape of the tapered portion R2 at the end of the light guide 1 is used. Forms a truncated cone, and has an upper base r1 = 3.2 mm, a lower base r2 = 4.5 mm, and a length L = 6 mm.
FIG. 11A shows the result of tracing the end ray at the end of the taper portion by simulation when this shape is used. Here, FIG. 11A shows the tracking result of the end ray, and FIG. 11B is an enlarged view showing the tracking result of the loss beam from the end slit at this time.
FIGS. 12A and 12B show simulation results of the illuminance distribution in the main scanning direction and the illuminance distribution in the sub-scanning direction at this time.
As is clear from these figures, although there is a portion with high illuminance at the end, the peak at the end is slightly lower than in the case of the conventional example, and the central portion of the light guide 1 The illuminance is improved. Moreover, although the simulation was similarly performed about the length direction, it turned out that uniform illumination intensity can be obtained.

  At this time, the total illuminance on the original surface is about 8000 lx and the efficiency is 20%, and an improvement in efficiency of 6% can be achieved as compared with the conventional case without the tapered portion.

Next, a second embodiment of the present invention will be described.
In Example 2, the length L of the tapered portion of the linear illumination device will be described.
In the first embodiment, the shape of the tapered portion R2 at the end of the light guide 1 is a truncated cone, and the upper base r1 = 3.2 mm, the lower base r2 = 4.5 mm, and the length L = 6 mm. An experiment was conducted for the case where the length L was changed.
The same simulation was performed with the length L of the tapered portion L = 5 mm and 4 mm. The linear illumination device of Example 2 has the structure shown in FIGS. 1 to 4 in Embodiment 1 as in Example 1, and has the same shape as Example 1 as shown in FIG. The shape of the tapered portion R2 at the end of the light guide 1 is a truncated cone, the upper base r1 = 3.2 mm, the lower base r2 = 4.5 mm, and the length L = 5 mm.

FIG. 13 shows a tracking result of the end ray obtained by tracing the end ray at the end of the taper portion in the case of using this shape.
14A and 14B show the simulation results of the illuminance distribution in the main scanning direction and the illuminance distribution in the sub-scanning direction at this time. Moreover, although the simulation was similarly performed about the length direction, it turned out that it is uniform.

Further, as shown in FIG. 15, it is formed so as to form a truncated cone shape having the same shape as in the first embodiment, and the shape of the tapered portion R2 at the end of the light guide 1 forms a truncated cone, and the upper base r1 = A linear illumination device using a light guide with 3.2 mm, lower base r2 = 4.5 mm, and length L = 4 mm was created.
FIG. 15 shows a tracking result of the end ray obtained by tracing the end ray at the end of the taper portion by simulation when this shape is used.
FIGS. 16A and 16B show the results of measuring the illuminance distribution in the main scanning direction and the illuminance distribution in the sub-scanning direction at this time by simulation. Moreover, although the simulation was similarly performed about the length direction, it turned out that it is uniform.
From these results, when L = 6mm, there is relatively much reflected light through the slit S among the emitted light at the end, so the end light quantity can be adjusted by changing the slit pitch while ensuring the end light quantity. It is effective.

On the other hand, in the case of L = 5, the amount of direct light that does not pass through the reflection by the slit S of the outgoing light at the end is slightly increased, and the end light amount is adjusted by changing the slit pitch while ensuring the end light amount. Is somewhat difficult.
Further, when L = 4, the direct light is dominant, so that the edge light amount can be secured, but it is difficult to adjust the edge light amount by changing the slit pitch.
From the above results, L = 6 mm is desirable because the end light amount can be adjusted with the slit pitch while securing the end light amount. Further, the slit width can be adjusted with respect to the light intensity depth.

Thus, when L = 6 mm, there is a portion with high illuminance at the end, but the peak at the end is slightly lower than in the case of the conventional example, and the center of the light guide The illuminance is improved.
The total illuminance on the original surface at this time was 8,000 lx and the efficiency was 20%, and an improvement in efficiency of 6% was achieved compared to the conventional case without a tapered portion.

Next, a third embodiment of the present invention will be described.
Next, using the light guide of Example 1 with L = 6 mm, the result of measuring the illuminance distribution in the main scanning direction and the illuminance distribution in the sub scanning direction when the slit is formed and the slit pitch is changed by simulation. Is shown in FIGS. 17 (a) and 17 (b).
In performing the simulation, it was assumed that the arrangement pitch of the slits S provided with the prism surfaces was 0.4 mm, and a part of the slits S continuously formed at this pitch was filled flat. That is, when the slit pitch is 2, it is considered that one of the five slits S formed continuously at a pitch of 0.4 mm is effectively present and the remaining four are not present. Similarly, it is considered that the slit pitch 1.6 is effectively one of four consecutive slits and the remaining three do not exist.
FIGS. 17A and 17B are diagrams showing the illuminance distribution in the main scanning direction and the illuminance distribution in the sub-scanning direction when the slit pitch is 2, where the original surface average illuminance is 8000 lx and the illuminance unevenness is ± 10%. It turns out that it is a grade.

Although not shown, similarly, the original surface illuminance distribution in the length direction when the slit pitches were 1.6, 2, and 2.4 were simulated. As a result, it was found that the document surface illuminance distribution in the length direction was more uniform when the slit pitch was 2 than when the slit pitch was 1.6 and 2.4, respectively.
From this result, it can be seen that sufficient illuminance can be obtained even in the central portion of the light guide. Further, the efficiency with respect to the total luminous flux emitted from the light source part R1 at the slit pitch 2 was about 20%.

Next, a fourth embodiment of the present invention will be described.
In the present embodiment, the document surface illuminance distribution was simulated when the shape of the light emitting portion R3 of the light guide 1 was changed. FIG. 18 is a diagram showing a cross-sectional shape of the light emitting portion R3, the outer side being both end portions and the inner side being a central portion, both being a combination of an ellipse and a circle, and being formed so that the center of the ellipse and the center of the circle coincide. ing. In this example, the slit forming surface is flat, and when the width of the central portion of this flat portion is 0.9 mm, the width of the end portion is 0.6, 0.9, 1.1, 1.3. The result of measuring the illuminance distribution on the original surface by simulation is shown.

  Further, the illuminance distribution on the document surface was measured by simulation when the width b of the edge was changed to 0.6, 0.9, 1.1, and 1.3, respectively. From this measurement result, the illuminance distribution varies when the edge width b is 0.6 and 1.3, whereas the edge width b is slightly uniform when 0.9 and 1.1 when the edge width b is 1.1. It has become.

  From this result, it was found that the document surface illuminance distribution was more uniform when the center was 0.9 and both ends were 1.1.

Next, a fifth embodiment of the present invention will be described.
In the present embodiment, the relationship between the illuminance and the position in the sub-scanning direction when the original position when the shape of the light emitting portion R3 of the light guide 1 is changed is 0 mm, 1 mm, and 2 mm from the surface of the platen in FIG. . FIG. 19 (a) shows an elliptical light emitting side of the light guide 1, and FIG. 19 (b) shows a circular shape of the light emitting side (in either case, the lower part of the light guide 1, ie, The shape on the side where the slit S is disposed is the circular shape already described. In the following description, for the sake of simplicity, it is simply described as “the light guide 1 is an ellipse”). From these comparisons, it can be seen that the illuminance unevenness is greatly reduced in the case of an ellipse. s1, s2, and s3 (see FIG. 20) show the results of measuring the illuminance at 0 mm, 1 mm, and 2 mm from the surface of the platen, respectively.
According to FIG. 19A, even if it is separated from the surface of the platen by about 2 mm, at the center position (that is, the position where the scattered light from the original is imaged on an image sensor not shown), there is sufficient original surface illumination. It can be seen that it is secured. That is, it can be seen that the light depth can be improved by making the light exit surface side of the light guide 1 into an elliptical shape. The deep depth of light in this way means that the parallelism of light is very high in the sub-scanning direction.
FIG. 20 shows the results of measuring the relationship between the main scanning direction position and the illuminance when the light guide is an ellipse and a circle when the light guide is 0 mm, 1 mm, and 2 mm from the platen surface. FIG. 20 (a) shows a light guide having an ellipse, and FIG. 20 (b) shows a circle. From these comparisons, it can be seen that the illuminance unevenness is greatly reduced in the case of an ellipse. Here, s1, s2, and s3 indicate the results of measuring the illuminance at 0 mm, 1 mm, and 2 mm from the platen surface, respectively.

  From the above results, it can be seen that uniform irradiation can be performed by using a linear light guide having an elliptical cross section.

(Embodiment 3)
In the first and second embodiments, the tapered portion R2 has a conical shape. However, in this embodiment, the tapered portion basically has a conical shape, but an optimized tapered surface is used. As shown in FIG. 21, it is a tapered part having a discontinuous part. FIG. 21A is a perspective view of a main part, FIGS. 21B to 21D are side views and cross-sectional views, and FIG. 21E is a side view. 21A is a perspective view seen from the direction D in FIG. 21E, FIG. 21B is a side view seen from the direction C in FIG. 21E, and FIG. 21 (e) is an AA cross-sectional view, and FIG. 21 (d) is a BB cross-sectional view of FIG. 21 (e).
In the present embodiment, while repeating simulations, the reflection surface of the tapered portion is optimized and the discontinuous portion is formed so that light from the light source is guided as far forward as possible.
According to this configuration, since most of the light can be taken into the light guide body, efficiency can be improved and high illuminance can be obtained.

(Embodiment 4)
In the first to third embodiments, the linear lighting device has been described. In the present embodiment, a two-dimensional lighting device will be described.
As shown in FIGS. 22 to 23, the light source substrate 24 on which the organic electroluminescence element is mounted and the light emitted from the light source substrate 24 are guided, and the light is further subjected to angle conversion to emit light to the outside. Between the light source 21 and the light source substrate 24 and the light guide 21, the cross-sectional area is larger on the light guide 21 side than on the light source substrate 24 side so as to guide the light from the light source substrate 24 to the light guide 21. And an optical path portion 25 configured as described above. FIG. 22 is a perspective view of the lighting device, FIG. 23A is a top view of the lighting device, FIG. 23B is a cross-sectional view taken along line AA of FIG. 23A, and FIG. FIG. 24 is a plan view of the light source substrate.
In addition, the back surface side of the light guide 21 constitutes an optical region 22 having projections and depressions, and light can be reflected and emitted to the surface side with substantially parallel light.
According to this configuration, light from the light source provided on the side surface can be uniformly extracted to the front side.

In addition, as the light source substrate 24, what formed the organic electroluminescent element on the board | substrate comprised with glass or resin is used. The light source substrate 24 has a structure in which light emitting elements of three colors of RGB are arranged as shown in a plan view in FIG.
The organic EL element may be a white light source by providing three colors of RGB.

  The light source substrate 24 is a bottom emission type, that is, an element region is formed on the substrate surface so as to emit from the substrate side. For this reason, nothing is arranged on the substrate side surface facing the element formation surface A, and the flatness is extremely high, so that the light source substrate 24 can be brought into close contact with the optical path portion 25. Since the close contact portion does not scatter light, the light emitted from the light source substrate 24 can be efficiently guided to the light guide plate.

In addition, the organic EL element provided on the light source substrate 24 may be a single element that is configured to be long, but it is preferably configured by a plurality of elements. In this way, even if there is a non-light emitting element, the amount of light can be covered by another element, and uniform light emission can be obtained.
Furthermore, the light source applied in this illumination device is not limited to the organic electroluminescence element, and it is needless to say that it can be applied to other light sources such as LEDs.

(Embodiment 5)
In the present embodiment, another two-dimensional illumination device will be described.
As shown in FIGS. 25 and 26, the light source substrate 34 on which the organic electroluminescence element is mounted and the light emitted from the light source substrate 34 are guided, and the light is further subjected to angle conversion to emit light to the outside. Between the light source 31 and the light source substrate 34 and the light guide 31, the cross-sectional area is larger on the light guide 31 side than on the light source substrate 34 side so that the light from the light source substrate 34 is guided to the light guide 31. The light guide 31 includes an optical path conversion unit 32 between the optical path unit 35, and the light emitted from the light source substrate 34 is an optical path. An angle conversion of 90 degrees is once performed by the conversion unit 32, and after the light is uniform in the longitudinal direction, the light path 31 further converts the optical path. FIG. 25 is a view showing the lighting device, in which (a) is a perspective view, (b) is an enlarged view of a main part of part A, FIG. 26 (a) is a top view of the lighting device, and FIG. FIG. 26A is a lower side view, and FIG. 26C is a right side view.
Note that the back surface side of the light guide 31 and the end surface of the optical path changing unit 32 (FIG. 25C) constitute an optical region having irregularities, and light can be reflected and emitted to the front surface side with substantially parallel light. it can.
According to this configuration, light from a light source provided on the side surface can be converted twice and extracted uniformly on the upper surface side.

Here, as the light source substrate, a substrate in which an organic electroluminescence element is formed on a substrate made of glass or resin is used. In the light source substrate 34, the organic electroluminescence element has a structure in which three colors of RGB are laminated. Thereby, also in the light guide 31, the three colors of light are layered with respect to the emission surface.
The organic EL element may be a white light source by providing three colors of RGB.

  As described above, according to the present invention, it is possible to provide a linear illumination device that can secure a sufficient amount of light on the original surface, has a uniform illuminance on the original surface, and a relatively large light intensity depth. It is extremely effective as a light source for a scanner, particularly as a small light source for illumination.

The figure which shows the linear illuminating device of Embodiment 1 of this invention. The figure which shows the principal part of the linear illuminating device of Embodiment 1 of this invention. The figure which shows the principal part of the linear illuminating device of Embodiment 1 of this invention. The figure which shows the optical area | region of the linear illuminating device of Embodiment 1 of this invention. The figure which shows the relationship between the slit width of the linear illuminating device of Embodiment 1 of this invention, and illumination intensity distribution. The figure which shows the relationship between the slit width of the linear illuminating device of Embodiment 1 of this invention, and illumination intensity distribution. 1 is an external view showing a scanner using the linear illumination device according to the first embodiment of the present invention. Sectional explanatory drawing of the scanner using the linear illuminating device of Embodiment 1 of this invention. The figure which shows the light guide of the linear illuminating device of Embodiment 2 of this invention. The figure which shows the shape of taper part R2 of a light guide The figure which shows the tracking result of the edge ray when L = 6, and the tracking result of the edge slit ray The figure which shows the illuminance distribution in the main scanning direction of the document surface, the illuminance distribution in the sub-scanning direction, and the figure which shows the result of having measured the length direction by simulation The figure which shows the tracking result of the edge ray when L = 5, and the tracking result of the edge slit ray The figure which shows the result of having measured the illuminance distribution in the main scanning direction of the original surface, and the illuminance distribution in the sub scanning direction by simulation The figure which shows the tracking result of the edge ray at the time of L = 4 and the tracking result of the edge slit ray The figure which shows the result of having measured the figure which shows the illuminance distribution of the main scanning direction of the original surface, and the illuminance distribution of the sub scanning direction by simulation The figure which shows the result of having measured the figure which shows the illuminance distribution of the main scanning direction of the original surface at the time of changing slit pitch, and the illuminance distribution of the sub scanning direction by simulation The figure which shows the cross-sectional shape of a light guide The figure which shows the result of having measured the illumination intensity distribution of the subscanning direction in the case of an elliptical light guide and a circular light guide The figure which shows the result of having measured the illuminance distribution of the main scanning direction in the case of an elliptical light guide and a circular light guide The figure which shows the illuminating device of Embodiment 2 of this invention, (a) is a perspective view, (b) is a C direction side view, (c) is AA sectional drawing of (e), (d) is (e) ) BB sectional view, (e) is a side view The perspective view of the illuminating device of Embodiment 3 of this invention. (A) is a top view of the illuminating device, (b) is a cross-sectional view taken along the line AA of (a), and (c) is an enlarged view of a main part of B part of (b). Plan view of the light source board of the illumination device The figure which shows the illuminating device of Embodiment 4 of this invention, (a) is a perspective view, (b) is a principal part enlarged view of A. (A) is a top view of the illumination device, (b) is a lower side view of (a), and (c) is a right side view of (b). The figure which shows the linear illuminating device of a prior art example The figure which shows the linear illuminating device of a prior art example

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light guide 2 Optical area 3 Circuit board 4 LED chip 5 Concave reflective surface 7 Reflective surface 21 Light guide 22 Optical area 24 Light source board 25 Optical path part 31 Light guide 32 Optical path conversion part 34 Light source board 35 Optical path part 100 Platen 101 Document 104a, 104b Light source 200 Rod lens array 201 Light receiving element R1 Light source part R2 Taper part R3 Light emitting part S Slit

Claims (24)

A light source;
A light guide body made of a transparent member that guides the light emitted from the light source, further converts the angle of the light, and emits the light to the outside;
Arranged between the light source and the light guide so as to guide the light from the light source to the light guide,
An optical path portion having a cross-sectional area configured to be larger on the light guide side than on the light source side;
A lighting device comprising: The lighting device according to claim 1,
The light source is provided at least at one end of the light guide;
The light guide has an optical region provided on a surface in a longitudinal direction and light emitted from the light source is incident on the inside of the light guide, and the light that has passed through the optical region is Including a light emitting portion configured to be emitted to the outside from one longitudinal surface facing the optical region,
An illumination device comprising a tapered portion, wherein the optical path portion is connected to the light emitting portion and the light source, and constitutes a tapered surface whose outer surface gradually spreads from the light source toward the light emitting portion. The lighting device according to claim 2,
The taper portion is a lighting device having a conical surface. The lighting device according to claim 2,
The taper portion is an illuminating device having a taper angle such that light from the center of the light source is incident on the optical region of the light emitting portion at an obtuse angle. The lighting device according to claim 2,
The said taper part is an illuminating device which is a taper part with a discontinuous part. A lighting device according to any one of claims 2 to 5,
The taper portion is a lighting device formed integrally with the light emitting portion. The illumination device according to any one of claims 2 to 6,
An illuminating device in which an outer surface of the tapered portion forms a reflective surface. The illumination device according to any one of claims 1 to 7,
The light guide in the light emitting part,
A lighting device whose cross section perpendicular to the longitudinal direction is elliptical. The lighting device according to claim 8,
The light guide has a cross section perpendicular to the longitudinal direction on the light exit surface side of the light exit section,
With an oval shape,
An illumination device that is a circle on the side facing the light exit surface. The lighting device according to claim 8 or 9, wherein
In the light emitting part of the light guide,
An illuminating device in which the focal point of the ellipse is provided in the optical region. It is an illuminating device in any one of Claim 2 thru | or 10, Comprising:
The illuminating device, wherein the optical region is a reflective surface. It is an illuminating device in any one of Claim 2 thru | or 10, Comprising:
The illuminating device, wherein the optical region is a surface having a high refractive index. The lighting device according to any one of claims 2 to 12,
The optical area is an illumination device including a slit constituting a prism. The lighting device according to claim 13,
The light emitting unit is an illuminating device configured such that the outer diameter decreases toward the center. The lighting device according to claim 14,
The lighting device is configured such that the width of the slit in the direction perpendicular to the longitudinal direction of the light guide decreases as it goes to the center. The lighting device according to any one of claims 1 to 15,
The lighting device in which the shape of the cut surface parallel to both end faces of the light guide is similar in all cut surfaces. The illumination device according to any one of claims 2 to 16,
The illuminating device whose longitudinal direction which the light from the said light emission part radiate | emits is a surface perpendicular | vertical with respect to both end surfaces. The lighting device according to any one of claims 1 to 17,
The lighting device, wherein the light source is a light emitting diode. The lighting device according to claim 18,
The light emitting diode is a lighting device mounted on a concave reflecting surface formed on a circuit board. The lighting device according to claim 19,
The concave reflection surface has an inverted truncated cone shape, and the light emitting diode is mounted on the bottom surface of the inverted truncated cone shape. 21. The lighting device according to any one of claims 18 to 20,
The lighting device is connected to the light guide so that the light emitting diode is optically matched with a transparent resin having the same refractive index as the light guide. The lighting device according to any one of claims 1 to 17,
The illuminating device, wherein the light source is an electroluminescent element. The lighting device according to any one of claims 1 to 12,
The light guide includes an angle conversion unit and is configured to emit two-dimensional light. The illumination device according to any one of claims 1 to 23 disposed as a light source for irradiating a document,
An optical system that transmits reflected light from the surface of the document;
A document reading device comprising: a light receiving element that receives the reflected light through the optical system.

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