Abstract:
An illumination apparatus includes an LED, a first lens unit provided above the LED and a cylindrical lens provided above the first lens unit. The first lens unit receives light from the LED and emits the light toward the cylindrical lens. The cylindrical lens emits the light to the outside.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a vehicle light using a light emitting diode (LED) or the like as a light source, and particularly relates to a vehicle light (a so-called daytime running light (DRL)) for allowing drivers of other vehicles, pedestrians and so on to visually recognize the existence of a vehicle during daytime. 
       BACKGROUND ART 
       [0002]    The DRL has been now standardized in Europe and so on, and is becoming standardized in the United States and other countries. As for broadening of light, a light source having light broadening in a right and left direction (horizontal direction) with respect to an upper and lower direction (vertical direction) is required. 
         [0003]    As a related-art daytime running light (DRL), there exists an illumination device in which a light emission amount and the number of light emissions in an LED array are changed so that light distribution becomes suitable for daytime running by reducing illumination of a high beam of a headlight (for example, refer to Patent Literature 1).  FIG. 14  is a view showing a related-art illumination device for daytime running described in Patent literature 1. 
         [0004]    In  FIG. 14 , the illumination device includes an LED array  11  in which plural LEDs are aligned and a lens  12 . Light emitted from the LED array  11  is collimated by the lens  12 . Light from LEDs close to an optical axis of the lens  12  becomes light in an optical axis direction, namely, a front direction, and light from LEDs apart from the optical axis of the lens  12  becomes light in a right and left direction, which are emitted from the lens  12 . The light distribution becomes suitable for daytime running light by adjusting the light amount of respective LEDs of the LED array  11 . 
         [0005]    There is also a device in which a line-shaped light source is formed by using a light guide plate (for example, refer to Patent Literature 2).  FIG. 15  is a view showing a related-art daytime running light described in Patent literature 2. In  FIG. 15 , the illumination device includes a high output LED  13  and a light guide plate  14 . The light guide plate  14  has prisms  15  formed at an end face thereof. 
         [0006]    Light emitted from the high output LED  13  is incident on the light guide plate  14  and propagates inside the light guide plate  14  while being totally reflected. When the light propagating inside the light guide plate  14  is incident on the prisms  15 , optical paths of part of the light are bent by the prisms  15 , therefore, the light is deviated from the total reflection condition and emitted to the outside of the light guide plate  14 . A light  16  is emitted from the entire light guide plate  14 . 
       CITATION LIST 
     Patent Literature 
       [0007]    PTL 1: JP-A-2 010-67417 
         [0008]    PTL 2: JP-A-2011-29781 
       SUMMARY OF INVENTION 
       [0009]    According to an embodiment of the present invention, an illumination device includes an LED, a lens unit provided above the LED and a cylindrical lens provided above the lens unit, in which the lens unit receives light from the LED and emits the light toward the cylindrical lens, and the cylindrical lens emits the light to the outside. 
         [0010]    The illumination device according to the present invention is provided with the first lens unit in which a lens and a total reflection prism are integrated and the cylindrical lens, in which broadening of light is formed in the upper and lower (vertical) direction and the right and left (horizontal) direction in a fixed range by the first lens unit, and broadening of light is further formed in the right and left direction by the second lens, and the first lens unit is apart frosts the cylindrical lens by a predetermined distance, thereby forming a light source having a uniform line shape when seen from the front. 
         [0011]    Most of the light incident on the lens in the emitted light from the LED is emitted to the front direction, and light leaking to the periphery is reduced by the total reflection prism to be light irradiated to the front direction, which forms an efficient light source. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0012]      FIG. 1A  is a view showing positions of illumination devices in a motor vehicle. 
           [0013]      FIG. 1B  is a cross-sectional view of an illumination device according to Embodiment 1. 
           [0014]      FIG. 2A  is a cross-sectional view showing a first lens unit in an XZ plane according to Embodiment 1. 
           [0015]      FIG. 2B  is a cross-sectional view showing the first lens unit in an YZ plane according to Embodiment 1. 
           [0016]      FIG. 3A  is a cross-sectional view of a second lens according to Embodiment 1. 
           [0017]      FIG. 3B  is a cross-sectional view of a second lens according to Embodiment 1. 
           [0018]      FIG. 3C  is a plan view of the second lens according to Embodiment 1, which is seen from a Z-axis direction. 
           [0019]      FIG. 4A  is a cross-sectional view of the illumination device according to Embodiment 1. 
           [0020]      FIG. 4B  is a view showing a positional relationship of overlapping of light between the first lens unit and the second lens. 
           [0021]      FIG. 5A  is a diagram showing intensity distribution of light emitted from the first and second lenses with respect to angles in a right and left direction according to Embodiment 1. 
           [0022]      FIG. 5B  is a diagram showing intensity distribution of light emitted from the first and second, lenses with respect to angles in an upper and lower directions according to Embodiment 1. 
           [0023]      FIG. 5C  is a diagram showing intensity distribution of light emitted from planar portions of the second lens and cylindrical lens portions with respect to angles in the right and left direction according to Embodiment 1. 
           [0024]      FIG. 6  is a cross-sectional view of a second lens according to Embodiment 2. 
           [0025]      FIG. 7  is a cross-sectional view showing the first lens unit in an YZ plane according to Embodiment 3. 
           [0026]      FIG. 8  is a cross-sectional view of an illumination device according to Embodiment 4. 
           [0027]      FIG. 9  is a cross-sectional view showing the first lens unit in the XZ plane according to Embodiment  4 . 
           [0028]      FIG. 10  is a cross-sectional view showing the first lens unit in the YZ plane according to Embodiment 5. 
           [0029]      FIG. 11  is a schematic view of an illumination device according to Embodiment 6. 
           [0030]      FIG. 12A  is a front view of the second lens according to Embodiment 7 of the present invention. 
           [0031]      FIG. 12B  is a front view of the second lens according to Embodiment 7 of the present invention. 
           [0032]      FIG. 12C  is a front view of the second lens according to Embodiment 7 of the present invention. 
           [0033]      FIG. 13A  is a cross-sectional view of an illumination device according to Embodiment 8. 
           [0034]      FIG. 13B  is a cross-sectional view of a first lens unit according to Embodiment 8. 
           [0035]      FIG. 13C  is a cross-sectional view of an A-A plane of the first lens unit in  FIG. 13B . 
           [0036]      FIG. 13D  is a cross-sectional view of a B-B plane of the first lens unit in  FIG. 13B . 
           [0037]      FIG. 14  is a view showing a related-art illumination device for daytime running described in Patent literature 1. 
           [0038]      FIG. 15  is a view showing a related-art illumination, device for daytime running described in Patent literature 2. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0039]    Problems in the related-art structure will be explained prior to the explanation of embodiments of the present invention. In the related-art structure, it is difficult to change an outer shape of an illumination device freely as an illumination device for a daytime running light. There is little degree of freedom in arrangement such that the illumination device is arranged, in a line shape at a front inclined part of a vehicle body so that other drivers and pedestrians can see the light easily. 
         [0040]    Also in the illumination device for the daytime running using a light guide plate, a line-shaped light source with excellent visibility and designability can be easily formed and the degree of freedom in arrangement is nigh. However, there is a problem that light efficiency is low. As a loss is caused when the light is incident on the light guide plate from the LED and a large loss is further caused when the light is taken from the light guide plate, the efficiency is generally extremely low. 
         [0041]    Hereinafter, embodiments of the present invention for solving the above problems in related art will be explained with reference to the drawings. An object of the present invention is to provide an illumination device which can be formed in a line shape with high light efficiency, high degree of freedom in arrangement and excellent visibility and designability. 
       Embodiment 1 
       [0042]      FIG. 1A  is a view showing positions of illumination devices  100  according to Embodiment 1 in a motor vehicle.  FIG. 1B  is a cross-sectional view of the illumination device  100  for daytime running of a vehicle according to Embodiment 1. 
         [0043]      FIG. 1A  is a top view of a front part of a motor vehicle  150 . The illumination devices  100  are arranged on the right and left of the front part, which are oblique portions at corners. Though the illumination, devices  100  are obliquely arranged, it is necessary to emit uniform light seen from, a principal surface. It is also necessary to broaden the light more in a horizontal direction. That is because there are people, other motor vehicles and so on in the horizontal direction. 
         [0044]    In  FIG. 1A  and  FIG. 1B , an upper side of the page is set as a Z-axis direction, a right direction is set as an X-axis direction and a depth direction of the page is set as a Y-axis direction as coordinate axes. The Z-axis direction corresponds to the front direction (a front part and a rear part of the motor vehicle), the Y-axis direction corresponds to an upper and lower direction (vertical direction) and the X-axis direction corresponds to a right and left direction.  FIG. 1A  and  FIG. 1B  are views seen from the same direction. 
         [0045]    In  FIG. 1B , each illumination device  100  includes an LED substrate  103 , first lens units  102  in the front direction (upper direction in the drawing) of the LED substrate  103  and a second lens  104  in the front direction (upper direction in the drawing) of the first lens units  102 . The illumination device  100  is inclined at an inclined angle a with respect to the X-axis (right and left direction). 
         [0046]    LEDs  101  are arranged on the LED substrate  103 . The LEDs  101  are arranged at approximately equal intervals on the LED substrate  103 . The front direction is the Z-axis direction and the LED substrate  103  is arranged so as to be inclined with respect to the front. The illumination devices  100  are obliquely arranged with respect to the front (Z-axis direction) as shown in  FIG. 1A . 
         [0047]    Light with a distribution close to perfectly diffused light is emitted from the LEDs  101 . One first lens unit  102  is provided so as to correspond to one LED  101 . The first lens unit  102  emits light with high directivity close to parallel light by using light emitted from the LED  101  as incident light. The second lens  104  is arranged almost in parallel to the LED substrate  103 , and a cylindrical lens array is formed on the LEDs  101  side (explained in  FIG. 3 ). The cylindrical lenses  123  are arranged so that the axial direction (longitudinal direction of a pillar shape) is parallel to the Y axis, and the light is diffused in an XY plane. 
         [0048]    (First Lens Unit  102 ) 
         [0049]      FIG. 2A  is a cross-sectional view showing a structure of the first lens unit  102 . The first lens unit  102  includes a first lens portion  105 , a second lens portion  107  and a triangular prism  106 . 
         [0050]    The first lens portion  105  is arranged so that, a lens central axis  109  is almost parallel to the Z-axis direction (front direction) and so that the center of a light emitting surface of the LED  101  corresponds to the vicinity of a focal position. 
         [0051]    The triangular prism  106  is positioned in a side surface of the first lens portion  105 . The triangular prism  106  includes three apexes with angles of 90 degrees, 45 degrees and 45 degrees. An optical path of light is changed by total reflection on a slope.  
         [0052]    The second lens portion  107  is positioned in an upper part of the triangle prism  106  as well as in the side surface of the first lens portion  105 . The second lens portion  107  is arranged so that a lens central axis  110  is almost parallel to the Z axis and so that the center of a light emitting surface of the LED  101  corresponds to the vicinity of a fecal position in consideration of an optical path length and the bending of the optical path due to the triangular prism  106 . 
         [0053]    The first lens  105  and the second lens  107  are preferably aspherical for reducing aberration. The first lens  105 , the triangular prism  106  and the second, lens  107  are integrally formed without an interface, and are formed of a transparent member such as glass, polycarbonate, acrylic or the like having the same refractive index. 
         [0054]    The LED  101  is arranged in the vicinity of the focal planes of the first lens  105  and the second lens  107  in the above description, and more specifically, the LED  101  is arranged with defocusing so that broadening of emitted light from the first lens  105  and the second lens  107  will foe broadening of light having a specified value in an upper and lower direction (Z-axis direction). 
         [0055]    A width of the first lens unit  102  in the X-axis direction is a size which is the same as or slightly larger than an LED pitch P when seen from the Z-axis direction, so that the first lens units  102  are arranged, without a gap when seen from the Z-axis direction. 
         [0056]    The first lens  105  and the second lens  107  have a shape in which sides of a right and left direction (X-axis direction) are cut so as to be perpendicular to the X axis. The light from the LED  101  does not reach the cut areas or little light reaches the areas. Portions overlapping the adjacent first lens unit  102  (seen from, the Z-axis) are cut. 
         [0057]      FIG. 2B  shows a cross section (a YZ plane) taken along A-A passing the central axis of the first lens  105  of the first lens unit  102 . It is found that the light from the LED  101  is collected to a fixed specified range. 
         [0058]    (Second Lens) 
         [0059]      FIG. 3A  shows a schematic cross-sectional view of the second lens  104 . The second lens  104  includes a substrate  116  and cylindrical lenses  123 . The substrate  116  is a transparent substrate having a fixed thickness and made of glass, polycarbonate, acrylic or the like. The cylindrical lenses  123  are arranged on the LEDs  101  side (Z-axis negative side) of the substrate  116  and a cylindrical, axis (central, axis) of the cylindrical lenses  123  is formed in parallel to the Y axis. The cylindrical lenses  123  are arranged at equal intervals so that a cylindrical lens forming area  125  is slightly smaller than a cylindrical lens pitch  124 . 
         [0060]    That is to say, there are planar portions  117  in which the cylindrical lenses  123  are not formed in the substrate  116 . The effect of broadening the light by the second lens  104  can be reduced by providing the planar portions  117  with respect to the cylindrical lens forming areas  125 . As a result, the broadening of light inside the XY plane can be reduced and the light amount in the Z-axis direction can be increased. However, the broadening of light in the XY plane (right and left direction) becomes too small when the planar portions  117  are too large, therefore, the ratio of the planar portion  117  with respect to the cylindrical lens pitch  124  is set to approximately 1 to 20%. 
         [0061]    The second lens  104  may be rotated with respect to the LED substrate  103  so that the cylindrical axis of the cylindrical lens  123  is slightly rotated around the Z axis. This is because the distribution of emitted light from, the second, lens  104  can be adjusted. That is, the cylindrical axis is not vertical but is inclined at the angle introduced below with respect to a line in which the LEDs  101  are aligned. 
         [0062]    Next, the reason why it is preferable that the second lens  104  is rotated around the 2 axis will be explained.  FIG. 3B  and  FIG. 3C  show the second lens  104  seen from the Z-axis direction.  FIG. 3B  shows a state or not being rotated, and  FIG. 3C  shows a state in which the second lens  104  is rotated around the Z axis at a rotation angle φ. 
         [0063]    When the cylindrical axis of the cylindrical lens  123  is rotated around the Z axis slightly at the rotation angle φ, the cylindrical lens pitch  124  of the second lens  104  inside the XY plane becomes 1/cos φ times after the rotation at the rotation angle φ, which is increased in appearance. 
         [0064]    As a result, a curvature radius of the cylindrical lenses  123  is increased and the effect of broadening the light inside the XZ plane by the second lens  104  is reduced. Accordingly, it is useful for the optical adjustment performed when it is desirable to slightly narrow the broadening of light in the XZ plane (right and left direction) and to increase the light amount in the Z-axis direction. 
         [0065]    However, when the rotation amount around the Z axis of the cylindrical axis of the cylindrical lens  123  is too large, a broadening component is generated also in the YZ plane (upper and lower direction) and a distortion occurs in the broadening of light, therefore, it is desirable that the adjustment amount is approximately 0 to 10 degrees. The adjustment amount is preferably 0 to 5 degrees. 
         [0066]    Here, a columnar lens or a cylindrical lens is preferable to be used as the cylindrical lens  123  as shown in  FIG. 1B  and  FIG. 3A . It is also preferable to use lenses having a columnar shape or a cylindrical shape, in which part of the lens is expanded in a radial direction. A lens having a polygonal shape in cross section can be used. The number of angles is preferably five or more. 
         [0067]    (Operation) 
         [0068]    The operation of the illumination device for daytime running configured as described above will be explained with reference to  FIG. 2A . 
         [0069]    Front rays of light  111  emitted to the Z-axis direction (front direction) from, the LED  101  are incident on the first lens unit  102  as shown in  FIG. 2A . As the center of the light emitting surface of the LED  101  is arranged in the vicinity of the focal position of the first lens  105 , the front rays of light  111  emitted from the first lens  105  will be light having broadening specified in the upper and lower direction (Y-axis direction). 
         [0070]    Oblique rays of light  132  emitted from the LED  101  in the same-manner having a component of an obliquely right upward direction (direction inclined from the Z axis to the X-axis direction) in the drawing are incident on the triangular prism  106 . The light incident on the triangular prism  106  is totally reflected on the prism slope 
         [0071]    (a. total, reflection surface  108 ) and incident on the second lens  107 . As the center of the light emitting surface of the LED  101  is arranged in the vicinity of the focal position of the second lens  107 , the oblique rays of light  132  emitted from the second lens  107  will be light having broadening specified in the upper and lower direction. (Y-axis direction). 
         [0072]    The broadening of light emitted from the first lens unit  102  has the specified value in the upper and lower direction (YZ plane) and right and left direction (XZ plane). The light emitted from, the first lens unit  102  is increased so that a broadening angle of light becomes a broader specified value by the cylindrical lenses  123  with respect to the right and left direction (XZ plane) by the second lens  104 . 
         [0073]    (Intervals of the First and Second Lenses) 
         [0074]    An interval L between the second lens  104  and the first lens unit  102  will be explained with reference to  FIG. 4A  and  FIG. 4B . 
         [0075]      FIG. 4A  is a cross-sectional view of the illumination device  100 . The drawing corresponds to  FIG. 1B .  FIG. 4B  is an enlarged view showing a positional relationship between the first lens unit  102  and the second lens  104  in  FIG. 4A . 
         [0076]    In the interval between the second lens  104  and the first lens unit  102 , it is considered that a light overlapping width w between adjacent first lens units  102  requires at least ¼ or more of the LED pitch P on the second lens  104  for recognizing light to be continuous in the X-axis direction when seen from the Z-axis direction (Expression 1). 
         [0077]    In order to allow the illumination device  100  to be recognized as a continuous line-shaped light source when the illumination device  100  is seen, it is necessary that lights from the first lens unit  102  overlap to some degree on the second lens  104 . Intervals between the first lens units  102  are seen dark if the lights do not overlap, therefore, overlapping of at least 1/10 or sore, preferably ¼ or more is necessary. 
         [0078]    When a half width at half maximum of the broadening angle of light from the first lens unit  102  is θ, the LED pitch in the X-axis direction is P, the distance between the first lens unit and the second lens in the Z-axis direction is the interval L and the overlapping width of light is W, a relation shown by an expression 2 is obtained. 
         [0000]        W&gt;P/ 4  (Expression 1)
 
         [0000]        W= 2×tan θ× L   (Expression 2)
 
         [0000]      2×tan θ× L&gt;P/ 4  (Expression 3)
 
         [0000]    can be obtained from Expressions 1 and 2. Accordingly, the interval L between the first lens unit  102  and the second lens  104  is 
         [0000]        L&gt;P /(8×tan θ)  (Expression 4)
 
         [0079]    For example, when the half width at half maximum of the first lens unit  102  is 7 degrees and the LED pitch in the X-axis direction is 10 mm, the interval L between the first lens unit  102  and the second lens  104  is L&gt;10/(8×tan 7°)≈10.2 mm, therefore, they are set with an interval of at least 10.2 mm or more. 
         [0080]    (Travelling Direction of Light) 
         [0081]      FIG. 5A  to  FIG. 5C  show distribution diagrams indicating the broadening of light.  FIG. 5A  snows the broadening of light in the right and left direction (in the XZ plane). The broadening angle in emitted light of the second lens  104  is wider than emitted light of the first lens unit  102 . 
         [0082]      FIG. 5B  shows the broadening of light in the upper and lower direction (in the YZ plane). The broadening of light in the upper and lower direction (in the YZ plane) is a broadening of a specified, value in the first lens unit  102 , and the light is directly transmitted in the second, lens  104 . The cylindrical lenses  123  of the second lens  104  are arranged at equal intervals. 
         [0083]      FIG. 5C  shows the broadening of light in the right and left direction (in the XZ plane) concerning respective cylindrical lenses  123  and the planar portions  117  of the second, lens  104  and combinations thereof. The light transmitted through the planar portion  117  where the cylindrical lenses  123  are not formed is a sharp light having the same broadening angle as the emitted light from the first lens unit  102 . On the other hand, the light transmitted through the cylindrical lenses  123  has a wider broadening angle. The broadening of light in the right and left direction (in the XZ plane) is formed by overlapping (combining) these two lights. 
         [0084]    As the light intensity is necessary particularly in the front direction (Z-axis direction) in the angle distribution of light, the light passing through the cylindrical lenses  123  is combined with the light passing through the planar portions  117  without the cylindrical lens, thereby adjusting the angle distribution easily. 
         [0085]    As the light emitted from the first lens unit  102  has the broadening angle, lights between the first lens units  102  which are adjacent on the second lens  104  overlap. The intensify distribution is alleviated by the light diffusion effect due to the cylindrical lenses  123  of the second lens  104 , therefore, the line-shaped light source can be recognized, when seen from the front direction (Z-axis direction). 
         [0086]    (Advantages) 
         [0087]    According to the above structure, the first lens units  102  in which the lens and the total reflection prism are integrated and the second lens  104  in which the cylindrical lens array is arranged are included, in which the broadening of light in the upper and lower direction is formed by the first lens units  102  and the broadening of light in the right and left direction is formed by the second lens  104 , and the distance between the first lens units  102  and the second lens  104  is sufficiently increased, thereby allowing the light source to be recognized in the line shape when seen from the front. 
         [0088]    Additionally, most of light incident on the lenses in emitted, light from the LEDs  101  is emitted in the front direction, and light leaking to the periphery is reduced by the total reflection prisms to be light irradiated in the front direction, thereby obtaining the efficient light source. 
       Embodiment 2  
     Pillar-Shaped Lens  123   
       [0089]    The cylindrical lenses  123  has been explained as the convex shape, however, almost the same effects in optical characteristics can be obtained when forming the cylindrical lenses  123  in a concave shape.  FIG. 6  is an enlarged cross-sectional view of another example of the cylindrical lens  123 . As shown in  FIG. 6 , the same effects can be obtained also when a flat portion  142  is formed in an apex, part of the cylindrical lens. The flat portion  142  is on an apex of the cylindrical lens  123 . The flat portion  142  is a surface parallel to the surface of the substrate  116 . The cylindrical lenses  113  are arranged without a gap. The length of the flat portion  142  is the same as the planar portion.  117  in  FIG. 3 . 
         [0090]    Although the cylindrical lenses  123  are formed on the LED  101  side in the substrate  116 , the cylindrical lenses  123  may be formed on the opposite side (outer side). It is also preferable that the cylindrical lenses  123  are arranged on both sides. 
         [0091]    A cross sectional shape of the cylindrical lens  123  may be a spherical surface shape or an aspherical surface shape. The structure is the same as the structure in Embodiment 1 except the above. 
       Embodiment 3 
     Modification of First Lens Unit, Y-axis Direction 
       [0092]    As the structure of the first lens unit  102 , the A-A cross section, in  FIG. 2A  is shown in  FIG. 2B . A modification example of that is shown in  FIG. 7 . As shown in  FIG. 7 , it is preferable that the direction of lights leaking from the LED  101  to the periphery is changed to the front direction by total reflection surfaces by using a triangular prism  112  and a triangular prism  114 , and that the broadening of light in the upper and lower direction is formed by the fourth lens  113  and a fifth lens  115  also in the A-A cross section. 
         [0093]    The triangular prisms  112 ,  114  and the fourth lens  113  and the fifth lens  115  can be integrally formed with the first lens  105 . A focal distance of the fourth lens  113  is almost the same as the focal distance of the first lens  105  including an optical path length of the triangular prism  112 . The focal position is also almost the same as that of the first lens  105 . 
         [0094]    Also in the fifth lens  115 , the focal distance is almost the same as that of the first lens  105  including an optical path length of the triangular prism  114 . The focal position is also almost the same as that of the first lens  105 . Consequently the broadening angles of emitted light in the fourth lens  113  and the fifth lens  115  are almost the same as that of the first lens  105 . 
         [0095]    The emitted light from the LED  101  can be collected more by adding the fourth lens  113  and the fifth lens  115  as well as the triangular prism  112  and the triangular prism  114  to the first lens unit  102 , therefore, the light efficiency can be improved. However, the width of the first lens unit in the upper and lower direction is increased when adding the fourth lens  113  and the fifth lens  115  as well as the triangular prism  112  and the triangular prism  114 . That is, the line width of the line-shaped, light source is increased. The structure is the same as the structure in Embodiment 1 except the above. 
         [0096]    The optical loss can be improved approximately 5 to 20% by providing the triangular prism  112  and the triangular prism  114  though depending on the opening size and the focal distance of the first lens  105 . 
       Embodiment 4  
     Modification of First Lens Unit  102 , X-axis Direction 
       [0097]    The case in which the inclined angle α of the illumination device  100  is large is shown in  FIG. 1  in Embodiment 1.  FIG. 8  shows a cross-sectional view of the illumination device  100  in the case where the inclined angle α is small in  FIG. 1B . 
         [0098]    The light from the LED  101  tends to be emitted, to positive and negative both sides in the X axis when the inclined angle α is approximately 0 to 30 degrees, therefore, the example of  FIG. 8  in which the triangular prisms are arranged on both sides is preferable. 
         [0099]    On the other hand, when the inclined angle α is large (larger than 30 degrees) as shown in  FIG. 1B  of Embodiment 1, it is desirable to dispose the triangular prism only on the side to which the light tends to be emitted. As the amount of emitted light from the LED  101  in the X-axis negative side is small, the triangular prism and the lens on the X-axis negative side are not provided. 
         [0100]      FIG. 8  is a cross-sectional view of the illumination device  100  configured when the inclined angle α is small.  FIG. 9  is a cross-sectional view of the first lens unit  102  of  FIG. 8 . 
         [0101]    The first lens unit  102  is provided with a triangular prism  121  and a third lens  122  also in the X-axis negative side. Accordingly, the optical loss from the LEDs  101  can be reduced. 
         [0102]    A focal distance of the third lens  122  is made to be almost the same as the focal distance and the focal position of the first lens  105  including an optical path length of the triangular prism  121 , therefore, the broadening angle of emitted light from the third lens  122  becomes almost the same as that of the first lens  105 . 
         [0103]    The emitted light from the first lens unit  102  has broadening when seen in the YZ plane, therefore, it is necessary to set the width of the second lens  104  to be wider than the width of the first lens unit  102  for preventing the loss of the light amount. When the width of the second lens is set to be the same width as the width of the first lens unit, the light amount of emitted light from the second lens is slightly reduced. The structure is the same as the structure in Embodiment 1 except the above. 
       Embodiment 5   
     Example Using Reflector 
       [0104]      FIG. 10  is a cross-sectional view corresponding to  FIG. 2B . As shown in  FIG. 10 , there are provided the first lens unit  102 , the second lens  104  and a reflector  133  with a high reflectivity on a side surface between these lenses. As the reflector  133 , for example, a mirror-finished aluminum plate can be arranged. Even when the second lens  104  having the same width as the first lens unit  102  is used, the width can be reduced with little variation in optical characteristics. The structure is the same as the structure in Embodiment 1 except the above. 
       Embodiment 6  
     Modification Example of First Lens Unit  102   
       [0105]    It is also possible to apply a structure in which only the first lens  105  is provided as the first lens unit  102  as shown in  FIG. 11  if the optical loss from the LED  101  is allowable.  FIG. 11  is a view corresponding to FIG  1 B. The example differs only in the shape of the first lens units  102 . The structure is the same as the structure in Embodiment 1 except the above. 
         [0106]    The first lens unit  102  is configured only by the first lens  105 . Accordingly, the shape is simplified and manufacturing costs can be reduced. 
         [0107]    Embodiment 7 
       Direction of Pillar-Shaped Lens  123   
       [0108]      FIG. 12A  to  FIG. 12C  are front view (Z-axis direction) of the second lens  104 . Diagonal lines indicate the axial direction (longitudinal direction) of the cylindrical lens  123 . As explained in  FIG. 1A  and the like, the axis of the cylindrical lens  123  is parallel to the Y axis. The axis is parallel to the Y axis even when the illumination device is inclined or curved as shown in  FIG. 12B  and  FIG. 12C . That, is for broadening light to a direction perpendicular to the Y axis (a horizontal direction). 
         [0109]    The light emitted from the first lens unit  102  converges at a fixed specified angle equally without directionality and is broadened in the horizontal direction by the second lens  104 . The above direction is determined for broadening light in the horizontal direction when the illumination device  100  is attached to a motor vehicle. The structure is the same as the structure in Embodiment 1 except the above. 
         [0110]    The first lens units  102  are arranged so as to correspond to shapes, namely, linear, oblique and curved shapes of the illumination device  100 . It is not necessary to align the arrangement direction of the first lens units  102  with the axial direction of the cylindrical lenses  123 . 
       Embodiment 8 
     Modification, of First Lens Unit  102   
       [0111]      FIG. 13A  to  FIG. 13D  show a modification of the first lens unit. The example has a structure different from the above embodiments in which the first lens unit  102  includes the spherical lens and the right-angled triangular prism.  FIG. 13A  is a cross-sectional view of the illumination device  100 .  FIG. 13B  is a cross-sectional view of a first lens unit  201 ,  FIG. 13C  is an A-A cross-sectional view of the first lens unit  201 .  FIG. 13D  is a B-B cross sectional view of the first lens unit  201 . 
         [0112]    As shown in  FIG. 13B , the following unit is used as the first lens unit  201 . There is provided a first lens  203  including a lens surface  206  (lower surface) having a cylindrical axis in the Y-axis direction, in which a cross section of an XZ plane is an aspherical surface and a lens surface  207  (upper surface) having a cylindrical axis in the X-axis direction, in which a cross section of a YZ plane is an aspherical surface. 
         [0113]    Moreover, there is provided a prism  205  having a total reflection surface  210  (side surface) with an aspherical surface shape in a cross section of the XZ plane. Furthermore, there is formed a second lens  204  including a lens surface  211  (upper surface) having a cylindrical axis in the X-axis direction, in which a cross section of the YZ plane is an aspherical surface. 
         [0114]    The lens surface  206  has the cylindrical axis in the Y-axis direction, and collects light inside the XZ plane. The lens surface  207  has the cylindrical axis in the X-axis direction and collects light inside the YZ plane. A focal position of the lens surface  207  is in the vicinity of the LED  101 , which is arranged at a defocused position so that emitted light from the first lens  203  has the broadening angle in the upper and lower direction (YZ plane). 
         [0115]    The focal position of the lens surface  206  is in the vicinity of the LED  101 , which is arranged at a defocused position so that a broadening angle of the emitted light from the first lens  203  in the right and left direction (XZ surface) becomes the same degree as that of the upper and lower direction (YZ plane). 
         [0116]    In the total reflection surface  210  of the prism  205 , a focal position is in the vicinity of the LED  101 , which is arranged at a defocused portion so that broadening of emitted light from the second lens  204  in the right and left direction (XZ plane) becomes the same degree as the broadening of the first lens  203  in the right and left direction (XZ plane). 
         [0117]    The lens surface  211  has the cylindrical axis in the X-axis direction and collects light in the upper and lower direction (YZ plane). A focal position of the lens surface  211  is in the vicinity of the LED  101 , which is arranged at a defocused position so that broadening of emitted light from the lens surface  211  in the upper and lower direction (YZ plane) has the same degree as that of the first lens  203  in the upper and lower direction (YZ plane). 
         [0118]    The same effects as Embodiment 1 can be obtained by using the first lens unit  201  having the above structure. Additionally, the directions acting on the collection of light in respective surfaces are separated to upper/lower and right/left, therefore, the broadening of light in the upper and, lower direction and in the right and left direction can be easily adjusted. 
         [0119]    It is also preferable that a columnar surface having the axis in the X-axis direction is added to the lens surface  206  to be a toroidal surface to give the effect of broadening light in the upper and lower direction to the lens surface  206  to some degree, thereby finely adjusting the broadening of light in the upper and lower direction also in the lens surface  206 . Similarly, it is also preferable that a columnar surface having the axis in the Y-axis direction is added to the lens surface  207  to be a toroidal surface to give the effect of broadening light in the right and left direction to the lens surface  207  to some degree. Similarly, it is also preferable that a columnar surface having the axis in the Y-axis direction is added to the lens surface  211  to be a toroidal surface to give the effect of broadening light in the right and left direction to the lens surface  211  to some degree. 
       Modification Example Through All Embodiments 
       [0120]    Though the LED  101  is used as the light source, an EL device, a halogen lamp and so on may be used. 
         [0121]    Though the second lens  104  is the parallel flat plate, a curved surface may be included. 
         [0122]    Though the LEDs  101  are linearly arranged on the flat-plate LED substrate  103 , it is also preferable to arrange LEDs on a flexible substrate to be arranged in a curved line. 
         [0123]    Though the light source unit including the LEDs  101 , the first lens units  102 , the LED substrate  103  and the second lens  104  is arranged inside the XZ plane (horizontal surface arrangement), it is also preferable to arrange the light source unit at an arbitrarily inclined angle by allowing the axis of the cylindrical lenses of the second lens  104  to be parallel to the Y axis (upper and lower direction) and the lens central axis  109  to be set in the front direction (Z-axis direction). 
         [0124]    When an anti-reflection film or a minute anti-reflection structure is formed in the first lens unit and the second lens unit other than the total reflection surface  108  of the triangular prism  106 , light intensity can be improved approximately 4% per one surface, 16% in four surfaces in total, though the costs are increased. 
         [0125]    Though the combination of the cylindrical lens and the planar-portion without the cylindrical lens is used for adjusting the broadening of light in the right and left direction (in the XZ plane) in the second lens, it is also preferable to apply, for example, a structure in which the planar portion is formed in an apex portion of the cylindrical lens. 
         [0126]    Though the total reflection of the triangular prism  106  in the first lens unit  102  is a fiat surface, it is also preferable that the surface is formed to be an aspherical surface with a parabola, an ellipse and the like in cross section and that the second lens  107  is formed as the cylindrical lens  123 . 
         [0127]    It is also preferable that the light source is shaped by a mask by arranging the mask, in on an emitting surface of the second lens  104  to limit the opening, though the light amount is reduced. 
         [0128]    Though the first lens  105 , the triangular prism  106  and the second lens  107  are integrally formed in the above description, it is also preferable that they are formed as different members and are bonded by a transparent adhesive having approximately the same refractive index. 
         [0129]    Though the first lens  105  has been explained, as the aspherical lens, a spherical lens may be used if illuminance unevenness due to the increase of aberration is allowed. 
         [0130]    Though the triangular prism  106  is formed as the right-angled triangular prism having apex angles of 90 degrees, 45 degrees and 45 degrees, the apex angles may be changed within a range in which the total reflection can be obtained. 
         [0131]    Though the slope of the triangular prism  106  is the total reflection surface, reflection surfaces may foe formed by vapor deposition of aluminum or silver. At this time, effects due to dirt can be eliminated though the reflectivity is reduced. 
         [0132]    Though the first lens  105  and the second lens  107  have been explained as center-symmetric lenses, the curvature may be changed in the XZ plane and the YZ plane. 
         [0133]    The illumination device gift ached to the motor vehicle has been explained as the example, however, the present invention can be applied to other devices. The present invention can be applied to illumination devices attached to a building and so on. It is particularly effective in the case where the device is required to be installed by being obliquely inclined. 
         [0134]    Embodiments 1 to 7 can be combined according to need. 
       INDUSTRIAL APPLICABILITY 
       [0135]    The daytime running light for the vehicle according to the present invention is the line-shaped light source having high light efficiency and some degree of directivity by using LEDs, which can be applied to illumination applications such as spot illumination which selects only particular object to be illuminated. 
       REFERENCE SIGNS LIST 
       [0136]      11  LED array 
         [0137]      12  lens 
         [0138]      14  light guide plate 
         [0139]      15  prism 
         [0140]      16  light 
         [0141]      100  illumination device 
         [0142]      101  LED 
         [0143]      102 ,  201  first lens unit 
         [0144]      103  LED substrate 
         [0145]      104  second lens 
         [0146]      105 ,  203  first lens 
         [0147]      106  triangular prism 
         [0148]      107 ,  204  second lens 
         [0149]      108 ,  210  total reflection surface 
         [0150]      109 ,  110  lens central axis 
         [0151]      111  front rays of light 
         [0152]      112  triangular prism 
         [0153]      113  fourth lens 
         [0154]      114  triangular prism 
         [0155]      115  fifth lens 
         [0156]      116  substrate 
         [0157]      117  planar portion 
         [0158]      121  triangular prism 
         [0159]      122  third lens prism 
         [0160]      132  oblique rays of light 
         [0161]      123  cylindrical lens 
         [0162]      124  cylindrical lens pitch 
         [0163]      125  cylindrical lens forming area. 
         [0164]      133  reflector 
         [0165]      142  flat portion 
         [0166]      150  motor vehicle 
         [0167]      205  prism 
         [0168]      206 ,  207 ,  211  lens surface