Patent Grant
8388202
This application claims the priority benefit under 35 U.S.C. §119 of Japanese Patent Application No. 2009-234437 filed on Oct. 8, 2009, which is hereby incorporated in its entirety by reference. This application is also related to and incorporates by reference the U.S. patent application Ser. No. 12/901,485 entitled Vehicle Light filed on same date, Oct. 8, 2010.
The presently disclosed subject matter relates to a vehicle light, and in particular, relates to a vehicle light having a light emitting diode (LED) serving as a light source and an optical system for controlling light distribution pattern of the light beams from the LED light source utilizing a light guide (being a lens body having an inner reflecting surface), thereby projecting illumination light with a low-beam light distribution pattern, for example.
Japanese Patent Application Laid-Open No. 2008-078086 discloses a vehicle light having a light emitting diode (LED) as a light source and a light guide for controlling the light distribution pattern of light beams from the LED.
The light guide disclosed in Japanese Patent Application Laid-Open No. 2008-078086 is made of a glass material, and in order to decrease the entire weight of the vehicle light, the inventors examined the light guide that was prepared by using a transparent acrylic resin. In this case, it was observed that color blurring occurred at the boundary of the light distribution pattern. When the acrylic resin was replaced with polycarbonate having a higher heat resistance than acrylic resin, it was observed that the color blurring (color shading) significantly occurred at the bright-dark boundary of the light distribution pattern.
When the light source utilizes an LED, the inside temperature of the vehicle light is increased by the heat generated from the LED, and accordingly, it may be helpful to form the light guide and the like from a high heat resistant, transparent material such as polycarbonate. However, the polycarbonate material can have variable refractive indices depending on the wavelength of entering light beam when compared with other transparent resin materials, resulting in occurrence of large chromatic dispersion. It should be noted that the chromatic dispersion means the dispersion of light of which phenomenon can occur for a material having various refractive indices depending on wavelengths of incident light beams.
Accordingly, if the light guide for forming a predetermined light distribution pattern is formed from such a polycarbonate material with large chromatic dispersion, the color blurring can be generated by projecting light beams with particular wavelengths due to the chromatic dispersion, at areas outside of the bright-dark boundary of the light distribution pattern. Accordingly, there is the problem in which the illumination light may have color shading.
If the illumination light has such color shading, when an object with monochromatic color is illuminated therewith, the object can be observed with different colors at different positions, thereby degrading the color rendering properties. Such color shading of illumination light due to chromatic dispersion may occur not only in the case where the polycarbonate material is used, but also in the cases where other transparent materials including glass, acrylic resin and the like are used for molding a light guide although the degree of occurrence may vary.
The presently disclosed subject matter was devised in view of these and other problems and features and in association with the conventional art. According to an aspect of the presently disclosed subject matter, a vehicle light can have a light guide (being a lens body having an inner reflecting surface) as an optical system for forming a predetermined light distribution pattern. The vehicle light can prevent the color shading of illumination light generated due to the chromatic dispersion of the light guide. As a result, the vehicle light can project the illumination light with less color shading while maintaining favorable color rendering properties.
According to another aspect of the presently disclosed subject matter, a vehicle light can include: a light source for emitting visible light at a plurality of wavelengths; and a lens body having a light incident surface, a reflecting surface, and a light exiting surface, in which light beams from the light source can enter the lens body through the light incident surface and be reflected by the reflecting surface in a predetermined direction to exit from the lens body through the light exiting surface so that the light beams exiting from the lens body can form illumination light with a predetermined light distribution pattern. In this configuration, the lens body can have a refractive optical path configured to direct the light beams emitted from the light source to or near the boundary of the light distribution pattern and refract the light beams by at least any one of the light incident surface and the light exiting surface, and the reflecting surface can include a refractive optical path reflecting portion configured to reflect the light beams passing through the refractive optical path, the refractive optical path reflecting portion being formed such that the light beams that have passed through the refractive optical path to be subjected to color separation at all the wavelengths can exit from the lens body through the light exiting surface to the boundary of or within the light distribution pattern that is formed by light beams that have passed through optical paths other than the refractive optical path.
According to the presently disclosed subject matter, the light beams that have passed through the refractive optical path of the lens body for projecting light beams on or near the boundary of the light distribution pattern and thereby have been subjected to color separation may not be projected outside of the light distribution pattern, but projected on the boundary of the light distribution pattern or within the light distribution pattern. This configuration, accordingly, can prevent the occurrence of color blurring outside of the boundary and reduce the generation of color shading of illumination light due to color blurring.
Furthermore, the light beams that have been emitted from a certain light emitting point of the light source and passed through the refractive optical path of the lens body for projecting light beams on or near the boundary of the light distribution pattern can be spread due to the color separation and by the refractive optical path that is configured to project color separated light beams to within the light distribution pattern inside the boundary. Accordingly, the light beams can be mixed with light beams that are emitted from other light emitting points of the light source and spread within the light distribution pattern. Therefore, although there may be an adverse effect by the color separated light beams projected within the light distribution pattern, this configuration can suppress such adverse effect on the chromaticity within the light distribution pattern and prevent the color shading of illumination light from occurring.
In the vehicle light configured as described above, the light source and the lens body can constitute a light source unit, and the vehicle light can include a plurality of the light source units. In this configuration, each of the light source units can have a different light distribution pattern, and the different light distribution patterns from the plurality of the light source units can be overlaid with each other to form a desired or required light distribution pattern for a vehicle light, thereby illuminating a pedestrian's side road with a wider range.
According to the presently disclosed subject matter, a plurality of light source units each having the light source and the lens body as described above can be combined to constitute a single vehicle light for forming the required light distribution pattern. Accordingly, the vehicle light can illuminate wider area with illumination light having less color shading.
In the vehicle light according to the presently disclosed subject matter, the vehicle light can have a front direction of a vehicle body where the vehicle light can be installed, and illumination light projected in a direction of 20 degrees to the pedestrian's side road side with respect to the front direction can have a color temperature of 5000 K or more in terms of a white chromaticity range, and a variation in chromaticity of the illumination light with respect to illumination light projected in the front direction in accordance with CIE color system can satisfy the conditions of Δx≦0.002 and Δy≦0.02. Furthermore, illumination light projected in a direction of 30 degrees to the pedestrian's side road side with respect to the front direction can have a color temperature of 5000 K or more in terms of the white chromaticity range, and a variation in chromaticity of the illumination light with respect to illumination light projected in the front direction in accordance with CIE color system can satisfy the conditions of Δx≦0.01 and Δy≦0.03. In addition, a variation in chromaticity of illumination light projected in a direction of 10 degrees to the pedestrian's side road side with respect to the front direction with respect to illumination light projected in the front direction in accordance with CIE color system can satisfy the conditions of Δx≦0.01 and Δy≦0.02.
The above conditions of the presently disclosed subject matter may be conditions for forming illumination light with less color shading and high color rendering properties. Accordingly, the vehicle light as configured above can project illumination light with less color shading, thereby suppressing the occurrence of color blurring near the boundary of the light distribution pattern.
In the vehicle light configured as described above, the light distribution pattern can have a bright-dark boundary at its upper edge, and the light incident surface can be formed of a flat plane and/or a concave surface that can form a non-refractive optical path configured not to refract light beams emitted from a predetermined edge point of the light source and the refractive optical path configured to refract the light beams. Furthermore, the reflecting surface can include a non-refractive optical path reflecting portion configured to reflect the light beams that have passed through the non-refractive optical path and the refractive optical path reflecting portion configured to reflect the light beams that have passed through the refractive optical path. In addition, the refractive optical path reflecting portion can include an upper refractive optical path reflecting portion disposed on the reflecting surface upper than the non-refractive optical path reflecting portion in a vertical direction of the lens body. Here, the upper refractive optical path reflecting portion can be configured such that light beams can exit in a direction slightly lower than light beams that pass through the non-refractive optical path and exit from the lens body when the light beams emitted from the light source are assumed to be green light beams.
In the above configuration, the vehicle light can have the non-refractive optical path that cannot refract light beams emitted from a predetermined light emitting point of the light source for forming the bright-dark boundary of the light distribution pattern. The visible light beams with smaller refractive indices than green light beams may be reflected and exit the lens body in an upper direction than the green light beams. However, in the presently disclosed subject matter, since the visible light beams can be reflected by the upper refractive optical path reflecting portion (which is disposed on an upper side with respect to the non-refractive optical path reflecting portion), the visible light beams can be projected on the bright-dark boundary of the light distribution pattern or within the light distribution pattern. Accordingly, even if the light beams are color separated, the light beams can be reflected by the upper refractive optical path reflecting portion to the direction of the bright-dark boundary of the light distribution pattern or the light distribution pattern. Then, the light beams can be mixed with other light beams emitted from other light emitting points of the light source, thereby preventing the color blurring from being generated outside of the bright-dark boundary and suppressing the color shading of illumination light. It should be noted that though the term “non-refractive optical path” may mean the optical path through which light beams cannot be subjected to refraction, as the narrowest sense, the term “non-refractive optical path” herein shall mean the optical path that serves as a standard with small refraction in which the chromatic dispersion needs not be taken into consideration, as the broader definition.
In the vehicle light configured as described above, the non-refractive optical path reflecting portion of the reflecting surface can include a lower refractive optical path reflecting portion disposed on the reflecting surface lower than the non-refractive optical path reflecting portion in a vertical direction of the lens body. Here, the lower refractive optical path reflecting portion can be configured such that light beams can exit in a direction slightly lower than the light beams that pass through the non-refractive optical path and exit from the lens body when the light beams emitted from the light source are assumed to be green light beams.
In the above configuration, the vehicle light can have the lower non-refractive optical path reflecting portion. The visible light beams with larger refractive indices than green light beams may be reflected and exit the lens body in an upper direction than the green light beams. However, in the presently disclosed subject matter, since the visible light beams can be reflected by the lower refractive optical path reflecting portion (which is disposed on a lower side with respect to the non-refractive optical path reflecting portion), the visible light beams can be projected on the bright-dark boundary of the light distribution pattern or within the light distribution pattern. Accordingly, even if the light beams are color separated, the light beams can be reflected by the lower refractive optical path reflecting portion to the direction of the bright-dark boundary of the light distribution pattern or the light distribution pattern. Then, the light beams can be mixed with other light beams emitted from other light emitting points of the light source, thereby preventing the color blurring from being generated outside of the bright-dark boundary and suppressing the color shading of illumination light.
In the vehicle light configured as described above, the lens body can include an auxiliary reflecting surface which is different from the reflecting surface, the auxiliary reflecting surface being disposed within optical paths through which light beams that have been incident on the light incident surface travel and reach the reflecting surface within the lens body.
By providing a plurality of reflecting surfaces within the lens body, the degree of freedom for disposing the light source can be increased.
In the vehicle light configured as described above, the light source may be an LED light source including a light emitting diode element and a wavelength conversion material.
When the light source utilizes the LED light source, the downsizing and energy saving of the vehicle light can be achieved.
In accordance with the presently disclosed subject matter, when a predetermined light distribution pattern is formed with an optical system including such a light guide (being a lens body with an inner reflecting surface), the color shading of illumination light due to chromatic dispersion of the light guide can be prevented, thereby providing the illumination light with higher color rendering properties.
These and other characteristics, features, and advantages of the presently disclosed subject matter will become clear from the following description with reference to the accompanying drawings, wherein:
A description will now be made below to vehicle lights of the presently disclosed subject matter with reference to the accompanying drawings in accordance with exemplary embodiments.
The lens body 10 can have a bottom 14 including a light incident surface 12, a reflecting surface 16 which is arranged near the rear side of the vehicle body (in the rear portion of the light), a light exiting surface 18 which is arranged near the front side of the vehicle body, and a top surface 20 which is arranged on top of the lens body 10. The lens body 10 can be defined by these surfaces and not-shown side surfaces.
The light incident surface 12 can be a surface that receives light beams emitted from the LED light source 30 so that the light beams can enter the lens body 10 therethrough. In the illustrated example, the light incident surface 12 can be formed by a slightly inclined surface with respect to the horizontal plane (not shown) toward the rear side of the vehicle body. The remaining surfaces of the bottom 14 other than the light incident surface 12 can be formed by horizontal planes.
The reflecting surface 16 can be a surface that can reflect light beams from the light source 30 via the light incident surface 12 to a predetermined direction, and can be formed as, for example, a part of a revolved paraboloid or the like. The reflecting surface 16 can be formed of an inner surface with total reflection property or a reflecting film adhered to the outer surface of the transparent lens body 10 with the reflecting film formed from metal such as aluminum.
The light exiting surface 18 can be formed of a vertical plane that is perpendicular to the horizontal plane, and can be a surface through which the light beams reflected by the reflecting surface 16 can exit.
The LED light source 30 can be a light source having one or a plurality of LED chips in a single package to emit white light beams. The LED light source 30 can have a planar light emitting surface 30A facing upward in a substantially vertical direction. For example, the LED light source 30 can include an InGaN-based LED chip 200 that emits blue light beams as an LED chip, a circuit board on which the LED chip 200 is mounted (see
The light source units 2B to 2D can have the same or similar configuration as or to that of the light source unit 2A. The vehicle light 1 can be provided with these light source units 2A, 2B, 2C, and 2D, and the light beams emitted from these light source units 2A to 2D can be overlaid over each other so as to form a light distribution pattern for a low beam as shown in
As shown in
As shown, the light distribution pattern P can be composed of a plurality of light distribution sub-patterns (light distribution sub-areas) PA to PD corresponding to the respective light source units 2A to 2D. For example, the light source unit 2A can form the light distribution sub-pattern PA for illuminating the narrow area near the center point of H-V lines (deviation degree from H and V lines=zero degrees). The light source units 2B and 2C can form the light distribution sub-patterns PB and PC for illuminating the broader area than the sub-pattern PA while overlapping with the sub-pattern PA, respectively. The light source unit 2D can form the largest light distribution sub-pattern PD covering the light distribution sub-patterns PA, PB, and PC. It should be noted that the correspondences between the light source units 2A to 2D and the light distribution sub-patterns PA to PD are not limited to the above example, as well as any desired light distribution pattern P can be formed in accordance with the intended use and specification of the vehicle light 1. The number of the light source units is not limited to four, but may be two, three, or five or more.
The light source units 2A to 2D can be formed on the basis of the same or similar optical design scheme. For example, the optical design scheme of the light source unit 2A can be achieved by the following. First, suppose the LED light source 30 emits white light beams from various portions of the light emitting surface 30A to various directions (where the white light beams can include light beams at visible wavelengths). In this case, the physical relationship of the LED light source 30 and the lens body 10 and the target illumination directions of the white light beams (target exiting directions when the white light beams exit from the lens body 10) can be determined so that the desired light distribution sub-pattern PA can be formed as shown in
The refracting angle at the light incident surface 12 and the light exiting surface 18 with respect to the incident angle can be determined by a refractive index corresponding to the material employed for forming the lens body 10. This value is used during the optical designing. If the refractive index can vary depending on the wavelength of light, a refractive index at a particular standard wavelength (hereinafter, referred to as a standard refractive index) can be used as an approximation which is assumed as a constant refractive index over the entire wavelengths of white light (visible range). In the present exemplary embodiment, the optical design scheme can be achieved by adopting the wavelength of green color, which is an approximate center wavelength of white light, as a standard wavelength, and the refractive index at the wavelength of green color as a standard refractive index, and assuming that the standard refractive index is constant over the entire wavelengths of white light. Based on these settings, the light incident surface 12, the reflecting surface 16, and the light exiting surface 18 of the lens body 10 can be designed in shape and the like so as to provide the light distribution sub-pattern PA as shown in
When the lens body 10 is formed of a transparent resin material, the refractive index thereof may vary at various wavelengths more than that of glass lens formed of an inorganic material. In particular, a polycarbonate material having superior transparency, heat resistance and weather resistance has a refractive index which can significantly vary at various wavelengths and generate large chromatic dispersion. In this case, if the optical design scheme is determined to provide the desired light distribution sub-pattern PA of
In general, the lens body 10 can enlarge and project the image of the light emitting surface 30A of the LED light source 30 to provide the light distribution sub-pattern PA on a virtual plane as shown in
In the above-mentioned optical design scheme, suppose the case where the actual chromatic dispersion occurring in the lens body 10 is taken into consideration. The white light beams emitted from the light emitting point 30B may contain light beams that pass through the light incident surface 12 and the light exiting surface 18 along an optical path without refraction at both the surfaces 12 and 18 (non-refractive optical path). These light beams can be projected to the target bright-dark boundary line CL by a certain vertical angle. The white light beams may contain light beams that pass through the light incident surface 12 and the light exiting surface 18 along an optical path with refraction at either the surface 12 or 18 (refractive optical path). In this case, the light beams other than the green light beams with the standard refractive index, namely, red and blue light beams with longer or shorter wavelength than the standard wavelength may be separated from the green light beams because of different refractive indices from the standard refractive index (in the case of green light beams). The separated light beams may be directed in different directions from that of the green light beams at the surface where the refraction of the lens body 10 occurs. As a result, part of the red or blue light beams may be projected to the upper area than the target bright-dark boundary line CL by an upward angle, thereby generating a color blurring area above the target bright-dark boundary line CL. Accordingly, the unintended illumination area Q can be formed above the target bright-dark boundary line CL as shown in
In view of the conventional optical design scheme where the optical designing is performed by adopting a constant standard refractive index with respect to the entire wavelengths of white light beams without considering the chromatic dispersion by the lens body 10, the presently disclosed subject matter can provide an adjustment (correction) by taking the chromatic dispersion of lens body 10 with regard to white light beams emitted from the light emitting point 30B of the light emitting surface 30A (or the variation in refractive index wavelength by wavelength) into consideration. Specifically, the physical relationship between the LED light source 30 and the lens body 10 that constitute the basic structure of the light source unit 2A and the structure of the lens body 10 (the shape and the like of the light incident surface 12, the reflecting surface 16, and the light exiting surface 18) can be adjusted (corrected) so that the color blurring (namely, the unintended illumination area Q) is prevented from being generated above the bright-dark boundary line CL.
For example, the polycarbonate material has an optical property that the longer the wavelength is within the wavelength range of approx. 380 nm to approx. 780 nm being the wavelengths of white light beams (visible range), the smaller refractive index is observed. For example, the polycarbonate material shows the refractive indices of 1.6115, 1.5855, and 1.576 at the wavelengths of 435.8 nm (blue), 546.1 nm (green), and 706.5 nm (red), respectively. In this case, if the standard shape for the light incident surface 12, the reflecting surface 16, and the light exiting surface 18 of the lens body 10 is designed, the standard wavelength is employed as 546.1 nm for green light beams as well as the standard refractive index of 1.5855 is set. Furthermore, to cope with the chromaticity dispersion by the lens body 10, the red light beams at 706.5 nm and the blue light beams at 435.8 nm can be considered as the longest wavelength and the shortest wavelength. Based on these light beams at the respective wavelengths, the light incident surface 12, the reflecting surface 16, and the light exiting surface 18 of the lens body 10 can be adjusted from the standard shape. It should be noted that these specific wavelengths may be changed according to the intended use, specification, material properties, and the like.
It should be noted that in the present exemplary embodiment the adjustment (correction) is made only on the reflecting surface 16, but the light incident surface 12 and the light exiting surface 18 remain to have the standard shape (flat plane) (that has been designed with the standard refractive index).
Further, the light exiting surface 18 of the lens body 10 can be formed of a vertical flat plane as described above, and the chromatic dispersion may not occur or may scarcely occur due to the horizontally collimated exiting light beams that have been reflected by the reflecting surface 16through the light exiting surface 18 toward the target bright-dark boundary line CL. Accordingly, in order to facilitate the understanding, it is assumed that the chromatic dispersion and color separation cannot occur by the light exiting surface 18 and the directions of light beams exiting through the light exiting surface 18 coincide with the directions of light beams reflected by the reflecting surface 16.
Hereinafter, a description will be given of how the adjustment (correction) of the shape of the lens body 10 is done. The lens body 10 of
In the lens body 10 of the present exemplary embodiment, the shape of the reflecting surface 16 has been designed by taking the chromatic dispersion into consideration.
In this case, as the white light beams X1 can be incident on the light incident surface 12 perpendicularly without refraction by the light incident surface 12 and the light exiting surface 18 of the lens body 10. Accordingly, the target direction is set to the same angular direction toward the target bright-dark boundary line CL. The shape of the reflecting surface 16 can be designed to be matched to the basic shape (position and gradient) so that the white light beams X1 incident on the reflecting surface 16 at the position T1 can be reflected by a certain angle toward the bright-dark boundary line CL along the optical path CLD1.
Please note that the light incident surface 12 can be adjusted in terms of inclination angle so that the position T1 (where the white light beams X1 that are not subjected to refraction at the light incident surface 12 can be reflected by the reflecting surface 16) can be disposed at substantially vertical center of the reflecting surface 16. By doing so, the incident angles (refraction angle) of the light beams (which are all reflected by the reflecting surface 16) at the light incident surface 12 can be set as small as possible, thereby suppressing the occurrence of the chromatic dispersion. Furthermore, the non-refractive optical path (the light beams can be incident on the light incident surface 12 without refraction) can include the position T1 which is the same or similar to the basic shape.
On the other hand, the white light beams X2 and X3 which are subjected to refraction at the light incident surface 12 can be incident on the light incident surface 12 forward or rearward with respect to the white light beams X1. The white light beams X2 and X3 can be controlled to be directed in a lower angular direction than that toward the target bright-dark boundary line CL depending on the magnitude of the chromatic dispersion (color separation) by that refraction. Then, the reflecting surface 16 at the upper and lower positions T2 and T3 than the position T1 can be designed such that the white light beams X2 and X3 entering the lens body 10 can be reflected by the reflecting surface 16 at the respective positions T2 and T2 to be projected in a lower angular direction than the angular direction of the bright-dark boundary line CL (being the optical paths CLD2 and CLD3).
As one example of the method for designing the reflecting surface 16 of the present exemplary embodiment by correcting the reflecting surface with the standard shape, there is an exemplary method in which the position T1 that is not corrected and has the same basic shape is allowed to serve as a reference point, and the points on the reflecting surface above the reference point are sequentially corrected as a corrected point. In this instance, one point of plural points can be corrected such that the reflecting surface 16 has an inclination by which the surface can reflect white light beams to the target illumination direction as corrected. Then, the determined inclination is applied to the area of the reflecting surface upper than that point, thereby correcting the upper area with a corrected inclination without the necessity of entire correction. Then, another further upper point can be corrected in the same way as above to correct that point as well as the upper area with a corrected inclination. This process is repeated until the end portion of the reflecting surface. The lower area than the position T1 can be corrected by repeating the above process, although the presently disclosed subject matter is not limited to this.
Specifically, a description will be given of how the white light beams X1, X2, and X3 emitted from the light emitting point 30B of the LED light source 30 can be projected through the lens body 10 if the shape of the reflecting surface 16 is designed by taking the chromatic dispersion into consideration as in the present exemplary embodiment.
The white light beams X1 can be perpendicularly incident on the light incident surface 12 where they are not subjected to refraction. Accordingly, while no chromatic dispersion (color separation) occurs, the white light beams X1 travel inside the lens body 10 to impinge on the reflecting surface 16 at the position T1. The white light beams X1 incident on the reflecting surface 16 can be reflected in a direction along the optical path CLD1 to be projected through the light exiting surface 18 in the angular direction of the target bright-dark boundary line CL. Namely, the optical paths of the white light beams X1, X2, and X3 are the examples when the refractive index is assumed to be a constant standard refractive index at the entire wavelengths of the white light beams. As mentioned above, the refractive index for green light beams is used as the standard refractive index. Accordingly, the green light beams G1 contained in the white light beams X1 can pass the same optical path as the white light beams X1 with or without the refraction and can be projected in the target angular direction of the bright-dark boundary line CL. Furthermore, the red and blue light beams other than green light beams contained in the white light beams X1 can pass the same optical path as the white light beams X1 because there are no refraction at the light incident surface 12 (and light exiting surface 18) and no color separation. Then, the red and blue light beams can be projected in the target angular direction of the bright-dark boundary line CL. By this configuration, the white light beams X1 that are emitted from the light emitting point 30B and perpendicularly incident on the light incident surface 12 can be projected in the angular direction of the target bright-dark boundary line CL while the light beams can remain white, thereby forming the bright-dark boundary line CL.
The white light beams X2 that are obliquely incident on the light incident surface 12 near the front side may be subjected to refraction, thereby generating chromaticity dispersion and then color separation within the lens body 10. In this case, the green light beams G2 contained in the white light beams X2 can impinge on the position T2 of the reflecting surface 16 while passing the same optical path as the white light beam X2 that has been determined with the constant standard refractive index. Then, the green light beams G2 can be reflected by the reflecting surface 16 in a lower angular direction than the optical path CLD2 to be projected in a lower angular direction than the target angular direction of the bright-dark boundary line CL.
On the other hand, the red light beams R2 contained in the white light beams X2 are represented by a dotted line disposed in the upper area in
Although the drawings do not illustrate optical paths for the blue light beams contained in the white light beams X2, the same phenomenon occurs. Namely, the blue light beams can be refracted by a different refractive angle and separated at the light incident surface 12 and travel through a different optical path from the white light beams X2 (green light beams G2). In this case, however, the blue light beams can be projected through the light exiting surface 18 in a lower angular direction than the white light beams X2 (green light beams G2) in the opposite direction from the red light beam R2. By setting the reflecting surface 16 so that the red light beams R2 can be projected in the certain angular direction equal to or lower than the target bright-dark boundary line CL, the blue light beams can be consequently projected in an angular direction sufficiently lower than the target bright-dark boundary line CL.
The white light beams X3 that are obliquely incident on the light incident surface 12 near the rear side may be subjected to refraction, thereby generating chromaticity dispersion and then color separation within the lens body 10. In this case, the green light beams G3 contained in the white light beams X3 can impinge on the position T3 of the reflecting surface 16 while passing the same optical path as the white light beam X3 that has been determined with the constant standard refractive index. Then, the green light beams G3 can be reflected by the reflecting surface 16 in a lower angular direction than the optical path CLD3 so as to be projected in a lower angular direction than the target angular direction of the bright-dark boundary line CL.
On the other hand, the blue light beams B3 contained in the white light beams X3 are represented by a dotted line in
Although the drawings do not illustrate optical paths for the red light beams contained in the white light beams X3, where the same phenomenon occurs. Namely, the red light beams can be refracted by a different refractive angle and separated at the light incident surface 12 and travel through a different optical path from the white light beams X3 (green light beams G3). In this case, however, the red light beams can be projected through the light exiting surface 18 in a lower angular direction than the white light beams X3 (green light beams G3) in the opposite direction from the blue light beam B3. By setting the reflecting surface 16 so that the blue light beams B3 can be projected in the angular direction equal to or lower than the target bright-dark boundary line CL, the red light beams can be consequently projected in an angular direction sufficiently lower than the target bright-dark boundary line CL.
As described above, the light source unit 2A according to the present exemplary embodiment can include the LED light source 30 that emit white light beams. Among the white light beams from the light emitting point 30B of the LED light source 30, light beams just like the white light beams X1 that can pass through the non-refractive optical path where the chromatic dispersion (color separation) cannot occur without refraction can be projected in the angular direction to the bright-dark boundary line CL, thereby being capable of forming the clear bright-dark boundary line CL. By forming the bright-dark boundary line CL with the white light beams X1, the chromaticity of the bright-dark boundary line CL can be held within the range of white.
On the other hand, as described above, the white light beams include the white light beams X2 and X3 that pass through the refractive optical path where the chromatic dispersion may occur due to the refraction. In this case, the target illumination directions that have been determined with the constant standard refractive index at the entire wavelengths of the white light beams can be set to the lower angular direction than the bright-dark boundary line CL. Accordingly, the red and blue light beams to be projected in the upper angular direction than the green light beams due to the chromaticity dispersion can be projected in the direction toward the bright-dark boundary line CL or in an angular direction lower than the direction to the CL. Namely, the light beams at the wavelengths where the color separation occurs can be projected to the light distribution sub-pattern PA on the lower side of the bright-dark boundary line CL and be mixed with other illumination light from light emitting points other than the light emitting point 30B in the light distribution pattern. Accordingly, any problem due to the chromatic dispersion, such as the unintended illumination area Q formed above the bright-dark boundary line CL, can be prevented, thereby suppressing color shading of illumination light.
In the above description, we have paid attention to the light beams emitted from the light emitting point 30B of the LED light source 30. However, needless to say, the white light beams emitted from other points near the light emitting point 30B (closer to the front side) can generate red and blue light beams upward than green light beams contained therein due to the chromatic dispersion. As discussed above, however, the shape of the reflecting surface 16 can be corrected in accordance with the above described manner, thereby being capable of projecting these light beams to the lower area than the bright-dark boundary line CL. Accordingly, the problem where the unintended illumination area Q is generated due to the color shading can be resolved. Furthermore, the light beams that are emitted from the adjacent light emitting points near the light emitting point 30B and subjected to color separation may not be concentrated at a certain point with the same color light beams while being spread to a certain degree to be mixed with the other light beams from the other light emitting points. This can suppress the color shading of illumination light within the light distribution sub-pattern PA.
Herein, the chromatic dispersion by the lens body 10 can be generated by the white light beams that are emitted from the light emitting points 30B and the like and be incident on the light incident surface 12 by a certain incident angle to pass through the refractive optical path. In this case, the light beams at various wavelengths by color separation due to the chromatic dispersion may be projected in various directions through the light exiting surface 18. In principle, in the presently disclosed subject matter, the white light beams passing through optical paths for directing the light to the area other than the edge area of the light distribution sub-pattern PA can be mixed with other light beams from other light emitting points, thereby suppressing the generation of the color shading of the mixed illumination light even when the color separation occurs.
On the other hand, like white light beams passing through the refractive optical path to the direction of the upper edge area of the light distribution sub-pattern PA, or on or near the bright-dark boundary line CL, the white light beams that pass through the refractive optical path to the direction near the right edge, left edge and lower edge of the light distribution sub-pattern PA may be color separated during the passing through the refractive optical path. In this case, it may be possible that part of light beams color separated with a particular wavelength range (for example, red light, blue light, or mixed light thereof) can be projected outside the edges, thereby generating color blurring.
In order to cope with this problem, the light beams projected outside the edges can be corrected in a similar manner to the light beams to be projected on the bright-dark boundary line CL so that the light beams color separated at entire wavelengths can be projected within the target light distribution sub-pattern PA. This can be done by correcting the reflecting surface 16 from its basic shape, thereby directing the color separated light beams onto other light beams within the target light distribution sub-pattern PA. Accordingly, the color blurring near the edges can be prevented, thereby suppressing the color shading of the illumination light.
It should be noted that the color separated light beams to be projected on the boundary portion of the light distribution sub-pattern PA including the bright-dark boundary line CL can be projected not only within the light distribution sub-pattern PA, but also to other area within the other light distribution pattern, thereby suppressing the color shading of the entire illumination light effectively. The color separated light beams can be used to enhance the whiteness of illumination light beams in a certain illumination area, thereby further effectively suppressing the color shading of the illumination light. Needless to say, the color separated light beams at various wavelengths can be directed to areas where the other light source units 2B to 2D project white brighter light beams.
The bright-dark boundary line CL be formed by the LED light source having wavelength conversion materials, since the light flux emitted from an LED chip may not be shielded, thereby enhancing the light utilization efficiency (energy utilization efficiency). Accordingly, such a vehicle light utilizing an LED light source for forming the bright-dark boundary line CL for a low beam light distribution pattern near the H line can be beneficial. For example, the LED light source 30 of
Namely, the light beams emitted from the light emitting point 30B as shown in
In order to facilitate the explanation, it is described that the white light beams X1 reflected at the position T1 can travel along the non-refractive optical path in the previous exemplary embodiment. Herein, the term “non-refractive optical path” may mean the optical path through which light beams cannot be subjected to refraction, as the narrowest sense. However, in some cases there is a necessity that the refraction at the light exiting surface 18 should be taken into consideration. Accordingly, the term “non-refractive optical path” herein shall mean the optical path that serves as a standard with small refraction in which the chromatic dispersion needs not be taken into consideration, as the broader definition.
The LED light source 30 of the present exemplary embodiment utilized a light source having average values of x=0.3179 and y=0.3255 (corresponding that having a color temperature of 6248K) though the actual chromaticity characteristics may slightly vary at various light emitting points. On the other hand, the comparative headlamp utilized an HID light source having average values of x=0.3362 and y=0.3509 (corresponding that having a color temperature of 5346K).
Although the chromaticity of the LED light source 30 of the present exemplary embodiment was different from that of the HID light source of the comparative headlamp, and accordingly the chromaticity of illumination light was different from each other, they satisfied the requirement of the statutory standard chromaticity range as determined as white illumination light.
In
As to the chromaticity,
As being clear from the above differences, the vehicle light 1 of the present exemplary embodiment can form a light distribution pattern with less color shading within a sufficiently small variation range from the 0-degree point (in front of the vehicle body) to the 30-degree point (left-side pedestrian way).
It should be noted that the chromaticity variation may depend on the individual specificity, but the chromaticity variation of the vehicle light 1 of the present exemplary embodiment can be controlled between the measured point L4 (20 degrees leftward) and the measured point L0 (0 degrees) within the ranges of Δx≦0.002 and Δy≦0.02. Accordingly, the chromaticity variation within this range between 0 degrees and 20 degrees leftward may be sufficient for actual use.
Further, the chromaticity variation of the vehicle light 1 of the present exemplary embodiment can be controlled between the measured point L6 (30 degrees leftward) and the measured point L0 (0 degrees) within the ranges of Δx≦0.001 and Δy≦0.03. At the same time, it is possible that the chromaticity variation of the vehicle light 1 be controlled between the measured point L2 (10 degrees leftward) and the measured point L0 (0 degrees) within the ranges of Δx≦0.01 and Δy≦0.02.
A description will now be given of another exemplary configuration of the light source units 2A to 2D of the vehicle light 1 of
For example, the light incident surface 12′ can be formed by a circular arc with a center 52 away from the light emitting point 30B of the LED light source 30 (here, the circular arc has a larger radius of curvature than a circular arc that is formed by the light emitting point 30B as a center). The center 52 of the circular arc can be set by connecting the light emitting point 30B and the position T1′ of the reflecting surface 16′ near its center. Accordingly, the incident angle at the light incident surface 12′ can be smaller than the case of the light source unit 2A of the first exemplary embodiment, thereby suppressing the chromatic dispersion at the light incident surface 12′ due to refraction more than the first exemplary embodiment.
The shape of the reflecting surface 16′ can be designed by taking the chromatic dispersion occurring in the lens body 10 into consideration. The white light beams X1′ among white light beams emitted from the light emitting point 30B in various directions can perpendicularly enter the light incident surface 12′ and cannot be subjected to refraction at the light incident surface 12′ and the light exiting surface 18. The target projection direction is the angular direction to the bright-dark boundary line CL. Accordingly, the shape (position and inclination) of the reflecting surface 16′ at the position T1′ can be formed so as to reflect the white light beams X1′ (or green light beams G1′) to the bright-dark boundary line CL along the optical path CLD1′.
On the other hand, the white light beams X2′ and X3′ can be subjected to refraction at the light incident surface 12′ due to certain incident angles with respect to the light incident surface 12′, and accordingly, the angular directions can be set lower than the target bright-dark boundary line CL depending on the magnitude of the chromaticity dispersion (color separation) due to the refraction. In this case, a constant standard refractive index is considered over the entire wavelengths of white light beams, and the shape of the reflecting surface 16′ can be designed so that the white light beams X2′ and X3′ (or green light beams G2′ and G3′) can be directed (reflected) to respective angular directions lower than the angular directions to the bright-dark boundary line CL (optical paths CLD2′ and CLD3′).
By this configuration, the chromatic dispersion at the light incident surface 12′ can be suppressed more than in the first exemplary embodiment. Accordingly, the color blurring above the bright-dark boundary line CL can be suppressed more, or alternatively, the generation of color blurring can be completely prevented. Taking this feature into consideration, the angular direction of the white light beams (green light beams) can be made smaller, resulting in less change in the shape of the reflecting surface 16′. This means the adverse affect for the light distribution provided by other illumination area than the bright-dark boundary line CL can be suppressed.
It should be noted that the light incident surface 12′ may be an elliptic arc as long as it has a concave surface when viewed from the light emitting point 30B to obtain the same advantageous effects. When the light incident surface 12′ is formed to have a spherical surface with the center of the light emitting point 30B, the light incident angle can be 0 degrees without refraction, meaning that the color separation cannot be occur with any incident angle. However, in this case, the light utilization efficiency can be maintained only when the reflecting surface is designed to be large enough to cover the light entering the spherical light incident surface. Accordingly, the lens body can be larger than the previous exemplary embodiments. In view of this, the convex curved surface may be a good choice in a well balanced manner between the light utilization efficiency and the entire size of the lens body. Furthermore, the radius of curvature of the light incident surface near the reflecting surface can be designed to be closer to the radius of curvature of a spherical surface with the center of the light emitting point 30B.
In this configuration, the light beams that are emitted from the LED light source 30 and enter the lens body 10 through light incident surface 12″ can be directed to the reflecting surface 16″ not directly, but via another reflecting surface 103. Namely, the light beams entering the lens body 10 can be projected through the light exiting surface 18 with two times reflection within the lens body 10. In the illustrated example, the reflecting surface 103 can be formed by depositing aluminum on an outer surface of the lens body 10 where to form the reflecting surface 103.
The light source unit 2A of this configuration shown in
The shape of the reflecting surface 16″ can be designed by taking the chromatic dispersion occurring in the lens body 10 into consideration. The white light beams X1″ among white light beams emitted from the light emitting point 30B in various directions can perpendicularly enter the light incident surface 12″ and cannot be subjected to refraction at the light incident surface 12″ and the light exiting surface 18. The target projection direction is the angular direction to the bright-dark boundary line CL. Accordingly, the shape (position and inclination) of the reflecting surface 16″ at the position T1″ can be formed so as to reflect the white light beams X1″ (or green light beams G1″) to the bright-dark boundary line CL along the optical path CLD1″.
On the other hand, the white light beams X2″ and X3″ can be subjected to refraction at the light incident surface 12″ due to certain incident angles with respect to the light incident surface 12″, and accordingly, the angular directions can be set lower than the target bright-dark boundary line CL depending on the magnitude of the chromaticity dispersion (color separation) due to the refraction. In this case, a constant standard refractive index is considered over the entire wavelengths of white light beams, and the shape of the reflecting surface 16″ can be designed so that the white light beams X2″ and X3″ (or green light beams G2″ and G3″) can be directed (reflected) to respective angular directions lower than the angular directions to the bright-dark boundary line CL (optical paths CLD2″ and CLD3″).
The light source unit 2A of the third exemplary embodiment can widen the selection degree of freedom for disposing the LED light source 30 with the plural reflecting surfaces (16″ and 103) for guiding the light beams within the lens body 10. Namely, the change of the positions of the light incident surface 12″ and the reflecting surface 103 can alter the position of the LED light source 30. Also in this case, the projection direction of green light beams travelling through a refractive optical path can be set to lower than the angular direction of the bright-dark boundary line CL by the specific shape of the reflecting surface 16″, thereby preventing the color blurring from being generated above the bright-dark boundary line CL.
It should be noted the number of reflection in the lens body is not limited to two, but may be three or more as long as the reflecting surface 16 can be formed to prevent the color blurring from being generated above the bright-dark boundary line CL.
As in the first exemplary embodiment, the second and third exemplary embodiments can prevent the generation of color shading near the boundary areas at left, right, and lower edges of the light distribution sub-pattern as in the first exemplary embodiment.
In the first to third exemplary embodiments, the non-refractive optical path through which light beams can travel without refraction is provided at approximate vertical center in the reflecting surface 16 (16′ and 16″), but the presently disclosed subject matter is not limited to this. For example, the non-refractive optical path can be disposed near the upper most portion or lowermost portion of the reflecting surface 16 (16′ and 16″).
In the first to third exemplary embodiments, the shape of the reflecting surface 16 (16′ and 16″) can be corrected from its basic shape, but the presently disclosed subject matter is not limited to this. Any action surface, namely, at least one surface selected from the group consisting of the light incident surface 12 (12′ and 12″), the reflecting surface 16 (16′ and 16″), and the light exiting surface 18 (18′) can be corrected from its basic shape.
In the first to third exemplary embodiments, the basic configuration of the lens body 10 can be set to enlarge and project the light emitting surface 30A of the LED light source 30, but the presently disclosed subject matter is not limited to this. For example, the basic configuration of the lens body 10 in the light source unit 2A of the first exemplary embodiment of
In this case, the basic shape of the lens body 10 may be such that the white light beams emitted from the rearmost end light emitting point 30B of the LED light source 30 can be directed to the bright-dark boundary line CL while the white light beams emitted from the foremost end light emitting point of the LED light source 30 can be directed to the lower edge of the light distribution sub-pattern PA. The basic shape of the lens body 10 can be designed such that the white light beams emitted from the foremost end light emitting point of the LED light source 30 may also be directed to the areas other than the lower edge of the light distribution sub-pattern PA with the areas needing to be brighter (near the upper edge).
In alternative exemplary embodiment, the reflecting surface and the like of the lens body 10 can be formed of a plurality of divided reflection areas including those for directing and spreading white light beams in a horizontal direction (vertically narrow areas) and those for directing and spreading white light beams in a vertical direction (horizontally narrow areas) wherein these areas are disposed in a zigzag fashion. In this manner, the white light beams from the near-by light emitting points can be projected to different areas and/or the white light beams from the separated light emitting points can be projected to the same areas. Accordingly, a plurality of light source units can form a single light distribution pattern by controlling the light distribution within a single light source unit or in conjunction with other light source units.
The light source unit of the first to third exemplary embodiments can have a lens body formed of polycarbonate or other material including glass, acrylic resin, and the like. Even when a material that generate chromatic dispersion is employed, the presently disclosed subject matter can be applied to these cases.
In the light source unit of the first to third exemplary embodiments, the polycarbonate material is used. In this case, the birefringence of the polycarbonate material may generate blurring of the bright-dark boundary. However, the presently disclosed subject matter can not only prevent the color shading of illumination light, but also reduce such blurring of the bright-dark boundary due to birefringence of the polycarbonate material. For example, when using polycarbonate material, a residual stress is large after molding, and the molded article may have a birefringence due to the photoelasticity of the material. The birefringence may affect the light beams entering the light incident surface 12 (12′ and 12″) obliquely, so that the light beams may be separated in a plurality of directions. When ignoring this birefringence and considering the simple designing with a constant standard refractive index, the light beams separated due to the birefringence can generate blurring of the bright-dark boundary. Even in this case, the specific design in which the light beams color separated as in the previous exemplary embodiments can be directed in certain angular directions within the light distribution pattern below the bright-dark boundary line. This can also suppress the blurring due to the birefringence.
In the first to third exemplary embodiments, the shape of the light exiting surface 18 is a flat plane and light beams reflected from the reflecting surface 16 (16′ and 16″) are not subject to refraction by the light exiting surface 18. However, even if the basic shape of the light exiting surface 18 is not a flat plane and light beams are subjected to refraction by the light exiting surface 18, the presently disclosed subject matter can be applied to obtain the specific advantageous effects.
Namely, any one of light incident surface, reflecting surface and light exiting surface can be formed to correct light beams having been color separated through the refractive optical path at any of the light incident surface and the light exiting surface so that the corrected light beams can be overlaid with other light beams within the desired light distribution pattern.
The vehicle light of the presently disclosed subject matter is not only applied to a low beam headlamp, but also a high beam headlamp, a fog lamp, a signal lamp, and other various vehicle lights.
It will be apparent to those skilled in the art that various modifications and variations can be made in the presently disclosed subject matter without departing from the spirit or scope of the presently disclosed subject matter. Thus, it is intended that the presently disclosed subject matter cover the modifications and variations of the presently disclosed subject matter provided they come within the scope of the appended claims and their equivalents. All related art references described above are hereby incorporated in their entirety by reference.
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