Abstract:
A lighting device such as a vehicle lighting device can be configured to be easily adapted to design changes in order to comply with various required or desired luminous intensity distributions. Light emitted from a light source at a large angle with respect to a main optical axis of the light source is more significantly condensed closer to the main optical axis than is the light emitted from the light source at a relatively smaller angle with respect to the main optical axis of the light source. The lighting device can include a lens which has a first lens cut and a second lens cut. The first lens cut can allow light emitted from the light source at a relatively smaller angle with respect to the main optical axis of the light source to pass therethrough. The second lens cut is arranged outside the first lens cut so as to condense light, emitted from the light source at a larger angle, close to the main optical axis of the light source.

Description:
[0001]    This application claims the priority benefit under 35 U.S.C. § 119 of Japanese Patent Application No. 2006-90949 filed on Mar. 29, 2006, which is hereby incorporated in its entirety by reference. 
       BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The presently disclosed subject matter relates to a lighting device which is configured such that light emitted from a light source at a larger angle with respect to the main optical axis of the light source is condensed more than light emitted from the light source at emission angles within a lesser predetermined range with respect to the main optical axis of the light source. In particular, the disclosed subject matter relates to a lighting device which is miniaturized and can be easily adapted to design changes in order to comply with various required or desired luminous intensity distributions. The lighting device can be applied to a vehicle lighting device and other lighting applications. 
         [0004]    2. Description of the Related Art 
         [0005]    Conventionally, a vehicle lighting device is known which is configured such that light emitted from a light source (being, for example, a light emitting diode) at a relatively large angle with respect to the main optical axis of the light source is condensed more than light emitted from the light source at a relatively smaller angle with respect to the main optical axis of the light source. Such a vehicle lighting device is disclosed in, for example, Japanese Patent Laid-Open Publication No. 2002-231013. 
         [0006]    In the vehicle lighting device disclosed in Japanese Patent Laid-Open Publication No. 2002-231013, light emitted from a light source at a relatively small angle with respect to the main optical axis of the light source is not reflected, but irradiated as a direct light. Light emitted at a relatively larger angle with respect to the main optical axis is condensed by a reflector (or a reflecting member) provided around the light source to be directed along the main optical axis for irradiation. 
         [0007]    The vehicle lighting device having this configuration can provide a required or desired luminous intensity distribution (or light distribution). 
         [0008]    Accordingly, when the vehicle lighting device is designed to provide a required or desired luminous intensity distribution, in order to condense the light emitted at a relatively large angle with respect to the main optical axis, a reflector is inevitably installed around the light source. 
         [0009]    This typically requires space for installing the reflector around the light source, which can result in a problem where the entire size of such a vehicle lighting device becomes unnecessarily large. Furthermore, the space between adjacent light sources are sometimes widened to a certain extent in order to secure space for installing respective reflectors. 
         [0010]    In addition to this, if the light source is replaced with another light source due to a design change, the reflector installed in a narrow space around the light source is inevitably changed in design in order to provide a required or desired luminous intensity distribution (light distribution). 
         [0011]    A description will now be given regarding the technology relating to conventional lighting devices with reference to the accompanying drawings. 
         [0012]      FIG. 1  is a diagram illustrating a light distribution standard for typical vehicle lighting devices. In  FIG. 1 , the letter “H” represents a horizontal line whereas the letter “V” represents a vertical line crossing the main optical axis of the vehicle lighting device. The symbol “5° U” represents a line located above with respect to the horizontal line by an angle of 5°, and the symbol “5° D” represents a line located below with respect to the horizontal line by an angle of 5°. The symbol “10° R” represents a line located rightward by an angle of 10° with respect to the main optical axis of the vehicle lighting device, and the symbol “10° L” represents a line located leftward by an angle of 10° with respect to the main optical axis of the vehicle lighting device. 
         [0013]    For example, in accordance with the light distribution standard for a rear fog lamp, the luminous intensity on the lines HL and VL in  FIG. 1  should be 150 cd or more. Furthermore, the luminous intensity within the area defined by the dotted line in  FIG. 1  should be set in the range of from 75 cd to 300 cd. 
         [0014]      FIG. 2  is a cross sectional view of a vehicle lighting device in the technical field related to the disclosed subject matter. In  FIG. 2 , the letter “S” represents an incandescent source, and the letter “CL” represents the main optical axis of the light source S. Furthermore, the letter “R” represents a reflector for reflecting part of light emitted from the light source S, “LS” represents a lens, and LC 1 , LC 2 , LC 3 , and LC 4  represent lens cuts formed on the lens LS. 
         [0015]    As shown in  FIG. 2 , light A′ emitted from the light source S is refracted by means of the lens cut LC 1  and passes through the lens cut LC 1  to be irradiated as diffused light A in the illumination direction (upper side in  FIG. 2 ). Light B′ emitted from the light source S is refracted by means of the lens cut LC 2  and passes through the lens cut LC 2  to be irradiated as diffused light B in the illumination direction. 
         [0016]    Furthermore, light C″ emitted from the light source S is reflected by the reflector R to become reflected light C′ which is approximately parallel to the main optical axis CL of the light source S. Then, the reflected light C′ is refracted by means of the lens cut LC 3  and passes through the lens cut LC 3  to be irradiated as diffused light C in the illumination direction. 
         [0017]    Furthermore, light D″ emitted from the light source S is reflected by the reflector R to become reflected light D′ which is approximately parallel to the main optical axis CL of the light source S. Then, the reflected light D′ is refracted by means of the lens cut LC 4  and passes through the lens cut LC 4  to be irradiated as diffused light D in the illumination direction. 
         [0018]      FIGS. 3A and 3B  are diagrams for illustrating luminous intensity distributions CA, CB, CC, and CD of light A, B, C, and D, respectively.  FIG. 3A  separately shows the luminous intensity distributions CA, CB, CC, and CD overlapped with each other.  FIG. 3B  is a diagram showing a total luminous intensity distribution obtained by synthesizing the luminous intensity distributions CA, CB, CC, and CD. 
         [0019]    The vertical axis represents a luminous intensity and the horizontal axis represents a horizontal angle (being an angle on the horizontal line H as shown in  FIG. 1 ) with respect to the main optical axis CL of the light source S shown in  FIG. 2 . For example, zero (0) degree on the horizontal line H corresponds to the points on the main optical axis CL of the light source S. 
         [0020]    In this vehicle lighting device, an incandescent lamp having a filament is used as a light source S. In this instance, the luminous intensities of lights A′, B′, C″, and D″ emitted from the light source S are almost uniform, and accordingly, the luminous intensity of lights A, B, C, and D which have passed through the lens LS are also uniform. 
         [0021]    As a result, in this vehicle lighting device, the luminous intensity distribution CB of the light B is almost the same as that obtained by shifting the luminous intensity distribution CA of the light A rightward. Furthermore, the luminous intensity distribution CC of the light C is almost the same as that obtained by shifting the luminous intensity distribution CB of the light B rightward. Also, the luminous intensity distribution CD of the light D is almost the same as that obtained by shifting the luminous intensity distribution CC of the light C rightward. 
         [0022]    As a result, the luminous intensity in the vicinity of the right edge of the specified range is as high as that around the center area (at an angle of 0°) of the specified range as shown in  FIG. 3B , therefore satisfying the standard value. 
         [0023]    A description will now be given regarding another technology in the same technical field of the disclosed subject matter. The vehicle lighting device described above used an incandescent lamp as a light source S as shown in  FIG. 2 . In this conventional vehicle lighting device, an LED having a high directivity is now used as a light source. 
         [0024]      FIG. 4  shows a luminous intensity distribution of the LED serving as a light source. In  FIG. 4 , the horizontal axis represents an angle with respect to the main optical axis of the LED, and the vertical axis represents a percentage of the luminous intensity of the LED. In particular,  FIG. 4  shows the relationship between the angle with respect to the main optical axis of the LED and the luminous intensity percentage when the luminous intensity on the main optical axis of the LED is assumed to be 100%. As shown in  FIG. 4 , the LED shows its luminous intensity distribution with a sharp peak on the main optical axis, and therefore, the luminous intensity at a larger angle with respect to the main optical axis is abruptly decreased. 
         [0025]      FIG. 5  is a cross sectional view of part of a vehicle lighting device in the technical field related to the disclosed subject matter. The shown light source S is an LED. 
         [0026]    In this vehicle lighting device of  FIG. 5 , light A′ is emitted from the light source S at a relatively small angle with respect to the main optical axis CL of the light source S. This light A′ is refracted by means of the lens cut LC 1  and passes through the lens cut LC 1  to be irradiated as light A in the illumination direction (upper side in  FIG. 5 ). 
         [0027]    Furthermore, light B′ is emitted from the light source S, and is refracted by means of the lens cut LC 2  and passes through the lens cut LC 2  to be irradiated as light B in the illumination direction. Specifically, the angle formed between the main optical axis CL and the light B′ is larger than that formed between the axis CL and the light A′. Furthermore, the angle at which the light B′ is refracted by means of the lens cut LC 2  is larger than that at which the light A′ is refracted by means of the lens cut LC 1 . In other words, the light B′ emitted from the light source S at the larger angle with respect to the main optical axis CL than the light A′ is more significantly condensed close to the main optical axis CL of the light source S than the light A′ is. 
         [0028]    Furthermore, light C′ is emitted from the light source S, and is refracted by means of the lens cut LC 3  and passes through the lens cut LC 3  to be irradiated as light C in the illumination direction. Specifically, the angle formed between the main optical axis CL and the light C′ is larger than that formed between the axis CL and the light B′. Furthermore, the angle at which the light C′ is refracted by means of the lens cut LC 3  is larger than that at which the light B′ is refracted by means of the lens cut LC 2 . In other words, the light C′ emitted from the light source S at the larger angle with respect to the main optical axis CL than the light B′ is more significantly condensed close to the main optical axis CL of the light source S than the light B′ is. 
         [0029]    Furthermore, light D′ is emitted from the light source S, and is refracted by means of the lens cut LC 4  and passes through the lens cut LC 4  to be irradiated as light D in the illumination direction. Specifically, the angle formed between the main optical axis CL and the light D′ is larger than that formed between the axis CL and the light C′. Furthermore, the angle at which the light D′ is refracted by means of the lens cut LC 4  is larger than that at which the light C′ is refracted by means of the lens cut LC 3 . In other words, the light D′ emitted from the light source S at the larger angle with respect to the main optical axis CL than the light C′ is more significantly condensed close to the main optical axis CL of the light source S than the light C′ is. 
         [0030]      FIGS. 6A and 6B  are diagrams illustrating luminous intensity distributions CA, CB, CC, and CD of light A, B, C, and D shown in  FIG. 5 , respectively.  FIG. 6A  separately shows the luminous intensity distributions CA, CB, CC, and CD overlapped with each other. FIG.  6 B is a diagram showing a total luminous intensity distribution obtained by synthesizing the luminous intensity distributions CA, CB, CC, and CD. 
         [0031]    In these drawings, the vertical axis represents a luminous intensity and the horizontal axis represents a horizontal angle (being an angle on the horizontal line H as shown in  FIG. 1 ) with respect to the main optical axis CL of the light source S (see  FIG. 5 ). For example, zero (0) degree on the horizontal line H corresponds to the points on the main optical axis CL of the light source S. 
         [0032]    In this vehicle lighting device, an LED having a high-level directivity is used as a light source S. Accordingly, as shown in  FIGS. 4 and 5 , the luminous intensities of the light B′, C′, and D′ which are emitted from the light source S at a relatively large angle with respect to the axis CL are significantly decreased as compared to the luminous intensity of the light A′ which is emitted from the light source S at a relatively smaller angle with respect to the main optical axis of the light source S. 
         [0033]    In this instance, as shown in  FIG. 5 , the width of the lens cut LC 1  through which the high luminous intensity light A′ passes is almost the same as those of the lens cuts LC 2 , LC 3 , and LC 4  through which the corresponding low luminous intensity light B′, C′, and D′ pass, respectively. 
         [0034]    Furthermore, as shown in  FIG. 6A , the luminous intensity distribution CB of the light B is formed on the right side of the luminous intensity distribution CA of the light A. Furthermore, the luminous intensity distribution CC of the light C is formed on the right side of the luminous intensity distribution CB of the light B. Also, the luminous intensity distribution CD of the light D is formed on the right side of the luminous intensity distribution CC of the light C. 
         [0035]    Namely, as shown in  FIG. 6A , the luminous intensity distribution CB of the light B is almost the same as that obtained by reducing the luminous intensity distribution CA of the light A by 50% and shifting it rightward. Furthermore, the luminous intensity distribution CC of the light C is almost the same as that obtained by reducing the luminous intensity distribution CB of the light B and shifting it rightward. Also, the luminous intensity distribution CD of the light D is almost the same as that obtained by reducing the luminous intensity distribution CC of the light C and shifting it rightward. 
         [0036]    As a result, the luminous intensity in the vicinity of the right edge of the specified range is insufficient in spite of unnecessarily high luminous intensity around the center area (at an angle of 0°) of the specified range as shown in  FIG. 6B . Accordingly, the standard value cannot be satisfied. In other words, as shown in  FIGS. 5 and 6B , the luminous intensities of the light C and D emitted at relatively large angles with respect to the main optical axis of the light source S are insufficient in spite of the unnecessarily high luminous intensity synthesized by the light A and B emitted along or closer to the main optical axis CL of the light source S. 
       SUMMARY 
       [0037]    In view of the above-described and other characteristics and problems, the presently disclosed subject matter has been developed to provide a lighting device such as a vehicle lighting device in which the space between adjacent light sources can be narrowed and which can be entirely miniaturized. 
         [0038]    The presently disclosed subject matter can also provide a lighting device such as a vehicle lighting device which can be easily adapted to design changes in order to comply with various required or desired luminous intensity distribution. 
         [0039]    According to one aspect of the presently disclosed subject matter a lighting device can include: a light source having a main optical axis; and a lens having a first lens cut and a second lens cut formed thereon, the first lens cut allowing first light emitted from the light source at emission angles within a predetermined range with respect to the main optical axis to pass therethrough, the second lens cut allowing second light, emitted from the light source at a larger emission angle with respect to the main optical axis than the first light, to pass therethrough. In this case, the second lens cut can be configured to provide a larger condensing degree to the second light received from the light source than the first lens cut provides to the first light received from the light source. 
         [0040]    According to this aspect, the second light emitted from the light source at a relatively large angle with respect to the main optical axis of the light source is condensed not by a reflector or the like disposed around the light source, but by the second lens cut of the lens arranged on the main optical axis of the light source to be closer to the main optical axis. 
         [0041]    Therefore, it is not necessary to provide a reflecting member around the light source. As a result, the space around the light source can be reduced. This can decrease the distance between adjacent light sources, thereby miniaturizing the entire lighting device. 
         [0042]    Furthermore, in comparison to devices that use a reflector, the lighting device can be easily adapted to design changes in order to comply with various required or desired luminous intensity distributions. 
         [0043]    In the above-described lighting device, the lens can have a third lens cut formed outside the second lens cut, and the third lens cut can provide a larger condensing degree than that of the second lens cut. 
         [0044]    In the disclosed subject matter, the term “condensing degree” means the degree in which light having passed through the lens (lens cut) is condensed in accordance with the refractive index of the lens material and the refractive index determined by the shape of the lens cut. 
         [0045]    In this configuration, the relatively low luminous intensity light which has passed through the second lens cut is overlapped with the relatively low luminous intensity light which has passed through the third lens cut. Furthermore, the second and third lens cuts can be configured such that the light which has passed through the second lens cut and the light which has passed through the third lens cut cross each other. Specifically, the second and third lens cuts can be configured such that the outer edge of the light which has passed through the third lens cut is included within the outer edge of the light which has passed through the second lens cut. 
         [0046]    As a result, the relatively low luminous intensity light which has passed through the second lens cut and the relatively low luminous intensity light which has passed through the third lens cut overlap each other to increase the luminous intensity at that overlapped area. 
         [0047]    In the above-described lighting device, the light source can emit a relatively high luminous intensity light around the main optical axis of the light source, and is configured such that the larger the angle at which the light is emitted with respect to the optical axis, the lower the luminous intensity of light from the light source is emitted. In this case, the width of the first lens cut through which the relatively high luminous intensity light passes can be wider than those of the second and third lens cuts through which relatively low luminous intensity light pass. 
         [0048]    In other words, the width of the first lens cut through which the relatively high luminous intensity light passes is wider than those of the second and third lens cuts through which relatively low luminous intensity light passes so that the high luminous intensity light does not enter the boundaries of adjacent lens cuts. 
         [0049]    As a result, reduction of the light utilization efficiency of the light source due to high luminous intensity light entering the boundaries of adjacent lens cuts and being irregularly reflected can be reduced. 
         [0050]    In other words, the light utilization efficiency of the light source can be improved as compared to the case where the lens cut through which a high luminous intensity light passes is relatively narrow. 
         [0051]    In the above-described lighting device, the second and third lens cuts can be configured such that the light which has passed through the second and third lens cuts is not directed to the center of the light which has passed through the first lens cut, but is directed to the outer edge of the light which has passed through the first lens cut. 
         [0052]    Specifically, the second and third lens cuts can be configured such that the peaks of the luminous intensity distribution curves of the light which has passed through the second and third lens cuts is not coincident with the peak of the luminous intensity distribution curve of the light which has passed through the first lens cut, but is located at position(s) different from the peak of the luminous intensity distribution curve of the light which has passed through the first lens cut (for example, a bottom area of the curve). 
         [0053]    As a result, insufficiency of luminous intensity of light emitted at a large angle with respect to the main optical axis of the light source can be prevented in spite of the unnecessarily high luminous intensity of the light emitted along or close to the main optical axis of the light source. 
         [0054]    In other words, even when a light source which has a high directivity is used, insufficiency of the luminous intensity of the light emitted at a larger angle with respect to the main optical axis of the light source can be prevented in spite of the unnecessarily high luminous intensity of the light emitted along or closer to the main optical axis of the light source. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0055]    These and other characteristics, features, and advantages of the disclosed subject matter will become clear from the following description with reference to the accompanying drawings, wherein: 
           [0056]      FIG. 1  is a diagram illustrating a light distribution standard of typical vehicle lighting devices; 
           [0057]      FIG. 2  is a cross sectional view of a vehicle lighting device in the technical field related to the disclosed subject matter; 
           [0058]      FIGS. 3A and 3B  are diagrams illustrating luminous intensity distributions CA, CB, CC, and CD of light A, B, C, and D from  FIG. 2 , respectively; 
           [0059]      FIG. 4  is a diagram illustrating a luminous intensity distribution for an LED serving as a light source used in a vehicle lighting device in the technical field related to the disclosed subject matter; 
           [0060]      FIG. 5  is a cross sectional view of part of a vehicle lighting device in the technical field related to the disclosed subject matter; 
           [0061]      FIGS. 6A and 6B  are diagrams illustrating luminous intensity distributions CA, CB, CC, and CD of light A, B, C, and D shown in  FIG. 5 , respectively; 
           [0062]      FIG. 7  is a perspective view of parts of an exemplary vehicle lighting device made in accordance with principles of the disclosed subject matter; 
           [0063]      FIG. 8  is a view showing a lens LS of the vehicle lighting device of  FIG. 7  when viewed from the light source side; 
           [0064]      FIG. 9  is a cross sectional view showing the light source S and the lens LS of the vehicle lighting device of  FIG. 7 ; 
           [0065]      FIGS. 10A and 10B  are diagrams illustrating luminous intensity distributions C 1 , C 2 , and C 3  of light L 1 , L 2 , and L 3  shown in  FIG. 9 , respectively; 
           [0066]      FIG. 11  is a cross sectional view showing the light source S and the lens LS of the vehicle lighting device similar to  FIG. 9 ; 
           [0067]      FIGS. 12A and 12B  are diagrams illustrating the luminous intensity distribution C 1  and luminous intensity distributions C 4  and C 5  of light L 4  and L 5  of  FIG. 11 , respectively; 
           [0068]      FIG. 13  is a diagram illustrating a luminous intensity distribution of another example of a vehicle lighting device made in accordance with principles of the disclosed subject matter; and 
           [0069]      FIG. 14  is a view showing a lens LS′ of another example of a vehicle lighting device made in accordance with principles of the disclosed subject matter when viewed from the light source side. 
       
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0070]    A description will now be given of exemplary embodiments made in accordance with principles of the presently disclosed subject matter with reference to the accompanying drawings. A first exemplary embodiment of a vehicle lighting device of the disclosed subject matter will be described. In this vehicle lighting device, an LED having a high directivity is used as a light source. Accordingly, as shown in  FIG. 4 , a typical LED shows its luminous intensity distribution with a sharp peak on the main optical axis, and therefore, the luminous intensity at a larger angle with respect to the main optical axis is abruptly decreased. 
         [0071]      FIG. 7  is a perspective view of parts of the exemplary vehicle lighting device made in accordance with principles of the disclosed subject matter.  FIG. 8  is a view showing a lens LS of the vehicle lighting device of  FIG. 7  when viewed from the light source side. 
         [0072]    The vehicle lighting device can include a lens LS having thirty five (35) lens cuts  1  through  35  formed thereon as shown in  FIGS. 7 and 8 . Specifically, the lens cuts  2 ,  22 ,  21 ,  24 ,  4 ,  9 ,  6 , and  7  are arranged around the lens cut  1 . The lens cuts  3 ,  23 ,  28 ,  27 ,  26 ,  29 ,  30 ,  25 ,  5 ,  10 ,  15 ,  14 ,  11 ,  12 ,  13 , and  8  are arranged further outside the lens cuts listed immediately above. The lens cuts  18 ,  17 ,  16 ,  19 , and  20  and the lens cuts  33 ,  32 ,  31 ,  34 , and  35  are arranged further outside the lens cuts listed above in an upward and downward direction, respectively. 
         [0073]      FIG. 9  is a cross sectional view showing the light source S and the lens LS of the vehicle lighting device of  FIG. 7 . As shown in  FIGS. 7 to 9 , the width of the lens cut  1  is wider than those of the lens cuts  2 ,  3 ,  4 , and  5 . 
         [0074]    In the vehicle lighting device in accordance with the exemplary embodiment of  FIG. 7 , as shown in  FIG. 9 , light L 1 ′ is emitted from the light source S at a relatively small angle with respect to the main optical axis CL of the light source S, or at emission angles within a predetermined range. This light L 1 ′ is refracted by means of the lens cut  1  and passes through the lens cut  1  to be irradiated as light L 1  in the illumination direction (upper side in  FIG. 9 ). In accordance with the disclosed subject matter, the range of the emission angle at which the light L 1 ′ is emitted may be +/−30 degrees with respect to the main optical axis CL. In a case where a light source with a high directivity such as an LED light source is used, the light emitted within this angular range may have a certain high luminous intensity. Accordingly, the light that is emitted from the high directivity light source enters the lens cut  1  and is not refracted too much, thereby satisfying a required or desired luminous intensity distribution. 
         [0075]    Furthermore, light L 2 ′ is emitted from the light source S, and is refracted by means of the lens cut  2  and passes through the lens cut  2  to be irradiated as light L 2  in the illumination direction. The angle formed between the main optical axis CL and the light L 2 ′ is larger than that formed between the axis CL and the light L 1 ′. Furthermore, the angle at which the light L 2 ′ is refracted by means of the lens cut  2  is larger than that at which the light L 1 ′ is refracted by means of the lens cut  1 . In other words, the light L 2 ′ emitted from the light source S at the larger angle with respect to the main optical axis CL than that of the light L 1 ′ is more significantly condensed close to the main optical axis CL of the light source S than is the light L 1 ′. 
         [0076]    Furthermore, light L 3 ′ is emitted from the light source S, and is refracted by means of the lens cut  3  and passes through the lens cut  3  to be irradiated as light L 3  in the illumination direction. Specifically, the angle formed between the main optical axis CL and the light L 3 ′ is larger than that formed between the axis CL and the light L 2 ′. Furthermore, the angle at which the light L 3 ′ is refracted by means of the lens cut  3  is larger than that at which the light L 2 ′ is refracted by means of the lens cut  2 . In other words, the light L 3 ′ emitted from the light source S at a larger angle with respect to the main optical axis CL than that of the light L 2 ′ is more significantly condensed close to the main optical axis CL of the light source S than is the light L 2 ′. 
         [0077]      FIGS. 10A and 10B  are diagrams illustrating luminous intensity distributions C 1 , C 2 , and C 3  of light L 1 , L 2 , and L 3  shown in  FIG. 9 , respectively.  FIG. 10A  separately shows the luminous intensity distributions C 1 , C 2 , and C 3  overlapped with each other.  FIG. 10B  is a diagram showing a total luminous intensity distribution obtained by synthesizing the luminous intensity distributions C 1 , C 2 , and C 3 . 
         [0078]    In these drawings, the vertical axis represents a luminous intensity and the horizontal axis represents a horizontal angle (being an angle on the horizontal line H as shown in  FIG. 1 ) with respect to the main optical axis CL of the light source S (see  FIG. 9 ). For example, zero (0) degree on the horizontal line H corresponds with the points on the main optical axis CL of the light source S. 
         [0079]    In the vehicle lighting device of  FIG. 7 , an LED having a high-level directivity is used as a light source S. Accordingly, as shown in  FIGS. 4 and 9 , as compared to the luminous intensity of the light L 1 ′ which is emitted from the light source S at a relatively small angle (i.e., at emission angles within a predetermined range) with respect to the main optical axis of the light source S, the luminous intensities of the light L 2 ′ and L 3 ′ which is emitted from the light source S at a relatively larger angle with respect to the axis CL is significantly decreased. 
         [0080]    In the vehicle lighting device as shown in  FIG. 9 , the lens can have a lens cut  3  formed outside the lens cut  2 , and the lens cut  3  can provide a larger condensing degree than that of the lens cut  2 . In other words, the relatively low luminous intensity light L 2  which has passed through the lens cut  2  is overlapped with the relatively low luminous intensity light L 3  which has passed through the lens cut  3 . Accordingly, the luminous intensity distribution C 2  of the light L 2  is overlapped with the luminous intensity distribution C 3  of the light L 3  as shown in  FIG. 10A . 
         [0081]    Specifically, the lens cuts  2  and  3  can be configured such that the light L 2  which has passed through the lens cut  2  and the light L 3  which has passed through the lens cut  3  cross each other. More specifically, the lens cuts  2  and  3  can be configured such that the outer edge of the light L 3  which has passed through the lens cut  3  is included within the outer edge of the light L 2  which has passed through the lens cut  2 . As shown in  FIG. 10A , the luminous intensity distribution C 3  of the light  3  is located within the area of the luminous intensity distribution C 2  of the light  2 . 
         [0082]    In the conventional vehicle lighting device as shown in  FIGS. 5 and 6 , the light C with a relatively low luminous intensity which has passed through the lens cut LC 3  and the outside light D also with a relatively low luminous intensity which has passed through the lens cut LC 4  do not appropriately overlap with each other for irradiation. In other words, the light C and light D do not overlap each other for the purpose of providing better irradiation characteristics in the specified or desired range of irradiation for the lighting device. 
         [0083]    Conversely, in the vehicle lighting device of  FIG. 9 , the light L 2  and the light L 3  emitted from the light source S with respective larger angles to the main optical axis CL can increase the luminous intensity at the area to be irradiated (C 2 +C 3 ) as shown in  FIG. 10B . 
         [0084]    Furthermore, the vehicle lighting device of  FIG. 9  can also be different from the conventional vehicle lighting device in that the width of the lens cut  1  through which the relatively high luminous intensity light L 1 ′ passes can be wider than those of the lens cuts  2  and  3  through which relatively low luminous intensity light L 2 ′ and L 3 ′ pass. 
         [0085]    In the conventional vehicle lighting device shown in  FIGS. 5 and 6 , the high luminous intensity light A and B may enter the boundaries of the adjacent two lens cuts LC 1  and LC 2 . In order to prevent the high luminous intensity light from entering the boundaries, in the vehicle lighting device of  FIG. 9 , the width of the lens cut  1  is wider than those of the lens cuts  2  and  3 . 
         [0086]    In the conventional vehicle lighting device as shown in  FIGS. 5 and 6 , the high luminous intensity light A′ and B′ are incident on the boundary between the adjacent two lens cuts LC 1  and LC 2  and the incident light is irregularly reflected. In this case, the light utilization efficiency is reduced to a certain level. However, in the vehicle lighting device of  FIG. 9 , this reduction in light utilization efficiency can be partially or totally prevented. In other words, as compared to the conventional vehicle lighting device (as shown in  FIGS. 5 and 6 ) in which the widths of the lens cuts LC 1  and LC 2  (through which the high luminous intensity light A′ and B′ is allowed to pass) are set relatively narrower, the utilization efficiency of light L 1 ′ from the light source S is increased (see  FIG. 9 ). 
         [0087]    Furthermore, the lens cuts  2  and  3  are configured such that the light L 2  and L 3  which has passed through the lens cuts  2  and  3 , respectively, is not directed toward the center of the light L 1  which has passed through the lens cut  1  (center of the luminous intensity distribution C 1 ), but is directed to the outer edge of the light L 1  (the outer edge of the luminous intensity distribution C 1  or the right side edge of the specified range (see  FIG. 10B )). 
         [0088]    In other words, the lens cuts  2  and  3  are configured such that the peaks of the luminous intensity distributions C 2  and C 3  of the light L 2  and L 3  are not coincident with the peak of the luminous intensity distribution C 1  of the light L 1 , but are located at the bottom area of the luminous intensity distribution C 1  of the light L 1 . 
         [0089]    In the conventional vehicle lighting device as shown in  FIGS. 5 and 6 , the luminous intensity (CA+CB) of the light A and B irradiated along the main optical axis of the light source S is excessively high whereas the luminous intensity (CC+CD) of the light C and D irradiated at relatively large angles with respect to the main optical axis CL of the light source S is insufficiently small. The vehicle lighting device of  FIG. 7  can prevent or diminish this problem. 
         [0090]    In other words, even when a high directivity LED light source S is used, the problem in which the luminous intensity of light irradiated at a relatively large angle with respect to the main optical axis CL of the light source S is insufficiently small, and the luminous intensity of light irradiated along the main optical axis of the light source S is excessively high, can be totally or partially prevented. 
         [0091]      FIG. 11  is a cross sectional view showing the light source S and the lens LS of a vehicle lighting device similar to  FIG. 9 . 
         [0092]    In the vehicle lighting device shown in  FIG. 11 , light L 4 ′ is emitted from the light source S, and is refracted by means of the lens cut  4  and passes through the lens cut  4  to be irradiated as light L 4  in the illumination direction (upward direction in  FIG. 11 ). Specifically, the angle formed between the main optical axis CL and the light L 4 ′ is larger than that formed between the axis CL and the light L 1 ′ (the emission angle within the predetermined range as described above). Furthermore, the angle at which the light L 4 ′ is refracted by means of the lens cut  4  can be larger than that at which the light L 1 ′ is refracted by means of the lens cut  1 . In other words, the light L 4 ′ emitted from the light source S at a large angle with respect to the main optical axis CL as compared to that of the light L 1 ′ is more significantly condensed close to the main optical axis CL of the light source S than is the light L 1 ′. 
         [0093]    Furthermore, light L 5 ′ is emitted from the light source S, and is refracted by means of the lens cut  5  and passes through the lens cut  5  to be irradiated as light L 5  in the illumination direction. Specifically, the angle formed between the main optical axis CL and the light L 5 ′ is larger than that formed between the axis CL and the light L 4 ′. Furthermore, the angle at which the light L 5 ′ is refracted by means of the lens cut  5  can be larger than that at which the light L 4 ′ is refracted by means of the lens cut  4 . In other words, the light L 5 ′ emitted from the light source S at a large angle with respect to the main optical axis CL as compared to the light L 4 ′ is more significantly condensed close to the main optical axis CL of the light source S than is the light L 4 ′. 
         [0094]      FIGS. 12A and 12B  are diagrams illustrating luminous intensity distributions C 1 , C 4 , and C 5  of light L 1 , L 4 , and L 5  shown in  FIG. 11 , respectively.  FIG. 12A  separately shows the luminous intensity distributions C 1 , C 4 , and C 5  overlapped with each other.  FIG. 12B  is a diagram showing a total luminous intensity distribution obtained by synthesizing the luminous intensity distributions C 1 , C 4 , and C 5 . 
         [0095]    In these drawings, the vertical axis represents a luminous intensity and the horizontal axis represents a horizontal angle (being an angle on the horizontal line H as shown in  FIG. 1 ) with respect to the main optical axis CL of the light source S (see  FIG. 11 ). For example, zero (0) degree on the horizontal line H corresponds to the points on the main optical axis CL of the light source S. 
         [0096]    In the vehicle lighting device, an LED having a high-level directivity is used as a light source S. Accordingly, as shown in  FIGS. 4 and 11 , as compared to the luminous intensity of the light L 1 ′ which is emitted from the light source S at a relatively small angle (i.e., at emission angles within a predetermined range) with respect to the main optical axis of the light source S, the luminous intensities of the light L 4 ′ and L 5 ′ which are emitted from the light source S at a relatively larger angle with respect to the axis CL are significantly decreased. 
         [0097]    As shown in  FIG. 11 , the lens can have a lens cut  5  formed outside the lens cut  4 , and the lens cut  5  can provide a larger condensing degree than that of the lens cut  4 . In other words, the relatively low luminous intensity light L 4  which has passed through the lens cut  4  is overlapped with the relatively low luminous intensity light L 5  which has passed through the lens cut  5 . Accordingly, the luminous intensity distribution C 4  of the light L 4  is overlapped with the luminous intensity distribution C 5  of the light L 5  as shown in  FIG. 12A . 
         [0098]    Specifically, the lens cuts  4  and  5  can be configured such that the light L 4  which has passed through the lens cut  4  and the light L 5  which has passed through the lens cut  5  cross each other. More specifically, the lens cuts  4  and  5  can be configured such that the outer edge of the light L 5  which has passed through the lens cut  5  is included within the outer edge of the light L 4  which has passed through the lens cut  4 . As shown in  FIG. 12A , the luminous intensity distribution C 5  of the light L 5  is located within the area of the luminous intensity distribution C 4  of the light L 4 . 
         [0099]    In the conventional vehicle lighting device as shown in  FIGS. 5 and 6 , the light C with a relatively low luminous intensity which has passed through the lens cut LC 3  and the outside light D which also has a relatively low luminous intensity and which has passed through the lens cut LC 4  do not overlap with each other for irradiation. Conversely, in the vehicle lighting device of  FIG. 11 , even when a high directivity LED light source S is used, the light L 4  and the light L 5  emitted from the light source S with respective large angles with respect to the main optical axis CL can increase the luminous intensity at the area to be irradiated (C 4 +C 5 ) as shown in  FIG. 12B . 
         [0100]    Furthermore, one aspect of the vehicle lighting device that can be different from the conventional vehicle lighting devices can be that the width of the lens cut  1  through which the relatively high luminous intensity light L 1 ′ passes can be wider than those of the lens cuts  4  and  5  through which relatively low luminous intensity light L 4 ′ and L 5 ′ pass. 
         [0101]    In the conventional vehicle lighting device shown in  FIGS. 5 and 6 , the high luminous intensity light A and B may enter the boundaries of the adjacent two lens cuts LC 1  and LC 2 . In order to prevent the light from entering these boundaries, in the vehicle lighting device of  FIG. 11 , the width of the lens cut  1  can be wider than those of the lens cuts  4  and  5 . 
         [0102]    In the conventional vehicle lighting device as shown in  FIGS. 5 and 6 , the high luminous intensity light A′ and B′ are incident on the boundary between the adjacent lens cuts LC 1  and LC 2 , and the incident light is irregularly reflected. In this case, the light utilization efficiency is reduced to a certain level. However, in the vehicle lighting device of the exemplary embodiment shown in  FIG. 11 , this reduction in light utilization efficiency can be prevented or diminished. In other words, as compared to the conventional vehicle lighting device (as shown in  FIGS. 5 and 6 ) in which the widths of the lens cuts LC 1  and LC 2  are set to be relatively narrow, the utilization efficiency of light L 1 ′ from the light source S can be increased (see  FIG. 11 ). 
         [0103]    Furthermore, in the vehicle lighting device of  FIG. 11 , the lens cuts  4  and  5  are configured such that the light L 4  and L 5  which has passed through the lens cuts  4  and  5 , respectively, is not directed toward the center of the light L 1  which has passed through the lens cut  1  (center of the luminous intensity distribution C 1 ), but is directed to the outer edge of the light L 1  which has passed through the lens cut  1  (the outer edge of the luminous intensity distribution C 1  or the left side edge of the specified range (see  FIG. 12B )). 
         [0104]    Specifically, the lens cuts  4  and  5  are configured such that the peaks of the luminous intensity distributions C 4  and C 5  of the light L 4  and L 5  are not made coincident with the peak of the luminous intensity distribution C 1  of the light L 1 . In this case, the lens cuts  4  and  5  can be configured such that the peaks of the luminous intensity distributions C 4  and C 5  of the light L 4  and L 5  are located at the bottom area of the luminous intensity distribution C 1  of the light L 1 , or alternatively, are located at a position at which the luminous intensity of the distribution C 1  is the same as the peak values of the distributions C 4  and C 5 . 
         [0105]    In the conventional vehicle lighting device as shown in  FIGS. 5 and 6 , the luminous intensity (CA+CB) of the light A and B irradiated along the main optical axis of the light source S is excessively high, whereas the luminous intensity (CC+CD) of the light C and D irradiated at relatively large angles with respect to the main optical axis CL of the light source S is insufficiently small. The vehicle lighting device of the exemplary embodiment shown in  FIG. 11  can prevent or diminish this problem. 
         [0106]    In other words, in the vehicle lighting device of  FIG. 11 , even when a high directivity LED light source S is used, effects such a the luminous intensity of light irradiated at a relatively large angle with respect to the main optical axis CL of the light source S being insufficiently small can be diminished or eliminated, even when the luminous intensity of light irradiated along the main optical axis of the light source S (the luminous intensity in the vicinity of the center of the specified area (see  FIG. 12B ) is excessively high. 
         [0107]    In the light distribution standard for a rear fog light as shown in  FIG. 1 , the vertical height is less than the horizontal width. Accordingly, if principles of the disclosed subject matter as shown in  FIG. 7  are applied to such a rear fog light, even when the LED, which has the abruptly decreased luminous intensity at a large angle with respect to the main optical axis, is used, it is possible to prevent or diminish the luminous intensity from being insufficient at the upper and lower edge areas of the specified range of the light distribution. 
         [0108]    In view of this, the light L 2  and L 3  is directed to the outer edge of the light L 1  (the outer edge of the luminous intensity distribution C 1  or the right side edge of the specified range (see  FIG. 10B )) as shown in  FIGS. 9 and 10A  and  10 B. Furthermore, the light L 4  and L 5  is directed to the outer edge of the light L 1  (the outer edge of the luminous intensity distribution C 1  or the left side edge of the specified range (see  FIG. 12B )) as shown in  FIGS. 11 and 12A  and  12 B. On the other hand, the light which has passed through the lens cuts  6 ,  11 , and  16  (see  FIGS. 7 and 8 ) is not directed to the upper edge of the specified range (in the vicinity of the position on the “5°U” line in  FIG. 1 ). In addition to this, the light which has passed through the lens cuts  21 ,  26 , and  31  (see  FIGS. 7 and 8 ) is not directed to the lower edge of the specified range (in the vicinity of the position on the “5°D” line in  FIG. 1 ). 
         [0109]    Specifically, the light which has passed through the lens cuts  6 ,  11 , and  16  (see  FIGS. 7 and 8 ) is directed to the center of the specified range (in the vicinity of the position on the horizontal line H in  FIG. 1 ). In addition to this, the light which has passed through the lens cuts  21 ,  26 , and  31  (see  FIGS. 7 and 8 ) is directed to the center of the specified range (in the vicinity of the position on the horizontal line H in  FIG. 1 ). 
         [0110]    In the above-described vehicle lighting device, the lens cuts  7 ,  8 ,  12 ,  13 ,  17 , and  18  of the right upper area of the lens LS, the lens cuts  22 ,  23 ,  27 ,  28 ,  32 , and  33  of the right lower area of the lens LS, the lens cuts  9 ,  10 ,  14 ,  15 ,  19 , and  20  of the left upper area of the lens LS, and the lens cuts  24 ,  25 ,  29 ,  30 ,  34 , and  35  of the left lower area of the lens LS (see  FIGS. 7 and 8 ) may be provided only with the diffusion function features, but not with the light directing function features. 
         [0111]    As a second exemplary embodiment of a vehicle lighting device made in accordance with principles of the disclosed subject matter, part of the lens cuts  7 ,  8 ,  12 ,  13 ,  17 , and  18  of the right upper area of the lens LS, the lens cuts  22 ,  23 ,  27 ,  28 ,  32 , and  33  of the right lower area, the lens cuts  9 ,  10 ,  14 ,  15 ,  19 , and  20  of the left upper area, and the lens cuts  24 ,  25 ,  29 ,  30 ,  34 , and  35  of the left lower area may be provided only with light directing function features. 
         [0112]    Specifically, the lens cut  7  of the right upper area of the lens LS and the lens cut  14  of the left upper area may be provided with light directing function features. 
         [0113]      FIG. 13  is a diagram illustrating a luminous intensity distribution of a vehicle lighting device in accordance with the second exemplary embodiment. Specifically,  FIG. 13  is a diagram showing a total luminous intensity distribution obtained by synthesizing the respective luminous intensity distributions C 1 , C 2 , C 3 , C 4 , C 5 , C 7 , and C 14  of the light which has passed through the lens cuts  1 ,  2 ,  3 ,  4 ,  5 ,  7 , and  14 , respectively. In this drawing, the vertical axis represents a luminous intensity and the horizontal axis represents a horizontal angle (being an angle on the horizontal line H as shown in  FIG. 1 ) with respect to the main optical axis CL of the light source S (see  FIG. 7 ). For example, zero (0) degree on the horizontal line H corresponds to points on the main optical axis CL of the light source S. 
         [0114]    In the vehicle lighting device in accordance with the second exemplary embodiment, the light which has passed through the lens cuts  2  and  3 , respectively, is directed to the outer edge of the light which has passed through the lens cut  1  (the outer edge of the luminous intensity distribution C 1  or the right side edge of the specified range) as shown in  FIG. 13 . In addition to this, the light which has passed through the lens cut  7  is directed to the outer edge of the light which has passed through the lens cut  1  (the outer edge of the luminous intensity distribution C 1  or the right side edge of the specified range). As a result, any insufficient luminous intensity at the outer edge of the luminous intensity distribution C 1  (the right side edge of the specified range) can be compensated. 
         [0115]    Furthermore, in the vehicle lighting device in accordance with the second exemplary embodiment, the light which has passed through the lens cuts  4  and  5 , respectively, is directed to the outer edge of the light which has passed through the lens cut  1  (the outer edge of the luminous intensity distribution C 1  or the left side edge of the specified range) as shown in  FIG. 13 . In addition to this, the light which has passed through the lens cut  14  is directed to the outer edge of the light which has passed through the lens cut  1  (the outer edge of the luminous intensity distribution C 1  or the left side edge of the specified range). As a result, any insufficient luminous intensity at the outer edge of the luminous intensity distribution C 1  (the right side edge of the specified range) can be compensated. 
         [0116]    It should be appreciated that the vehicle lighting device in accordance with the first exemplary embodiment has a single light source S as shown in  FIGS. 7 and 8 . However, the disclosed subject matter is not limited thereto and may have a plurality of light sources. 
         [0117]      FIG. 14  is a diagram showing a lens LS′ of a vehicle lighting device in accordance with another exemplary embodiment of the disclosed subject matter when viewed from the light source side. In this case, four light sources can be provided (not shown). The lens LS′ may have four lens portions LS- 1 , LS- 2 , LS- 3 , and LS- 4  each having the same configuration as that of the lens LS of the vehicle lighting device of  FIG. 8 . 
         [0118]    In the vehicle lighting device of  FIG. 14 , the light emitted from the light source at a large angle with respect to the main optical axis is condensed close to the main optical axis of the light source S, not by a reflector, but by the lens cut of the lens LS′ located on the main optical axis of the light source. 
         [0119]    Accordingly, as compared with the case in which the reflector is used to collect light, the space around the light source can be reduced. Therefore, the lens portions LS- 1 , LS- 2 , LS- 3 , and LS- 4  can be located in close proximity to each other. 
         [0120]    In other words, the space between adjacent light sources can be narrowed, thereby miniaturizing the entire vehicle lighting device. 
         [0121]    Furthermore, in the vehicle lighting device of the exemplary embodiment shown in  FIG. 14 , a single substrate may be used to support the plurality of light sources. 
         [0122]    The disclosed subject matter can facilitate design change as compared to the case where a reflector is used for condensing light in order to make the design suitable for a required or desired luminous intensity distribution. 
         [0123]    In the illustrated exemplary embodiments, thirty four (34) lens cuts  2  through  35  are arranged around the lens cut  1 . However, the disclosed subject matter is not limited to this description. Alternatively, any number of lens cuts can be arranged around the lens cut  1 . 
         [0124]    In the illustrated exemplary embodiments, four (4) light sources are used. However, the disclosed subject matter is not limited to this description. Alternatively, any number of light sources can be arranged in line, in matrix, or the like fashion. 
         [0125]    The illustrated exemplary embodiments can also be combined appropriately and as desired without departing from the spirit and scope of the disclosed subject matter. 
         [0126]    While there has been described what are at present considered to be exemplary embodiments of the disclosed subject matter and invention, it will be understood that various modifications may be made thereto, and it is intended that the appended claims cover such modifications as fall within the true spirit and scope of the invention.