Illuminating device with a light distributing lens

Abstract: A lens (10) for a light distribution has an incident surface (11) and an exit surface (12), where the exit surface is an aspheric surface so that an aberration of the outer periphery (B) in the horizontal direction can be larger than an aberration of the outer periphery (B) in the vertical direction of the exit surface. Among light distributions formed by an outgoing light emitted from the exit surface (12), a light distribution in the horizontal direction blurs on the peripheral portion but a light distribution in the vertical direction does not blur on the peripheral portion.

Description: The present invention relates to an illuminating device for a vehicle according to the preamble of claim 1. Conventionally, a headlamp for a vehicle, in which a light distribution can obtain a desired dispersion in the right and left directions without blurring the boundary between bright and dark portions on the upper edge of the illumination pattern, has been proposed in JP-B-4-10163. This is designed to obtain a light distribution dispersing in the right and left directions of a vehicle with a projecting lens by projecting forward a shading edge of a light reflected by a reflective mirror. However, in such a construction, the outline of a light distribution or illumination pattern in the right and left directions of a vehicle is so clear that sufficient dispersion cannot be obtained. Further, the boundary between the bright and dark portions of the upper edge becomes unclear, it causes glaring against the on-coming vehicles running on the opposite lane. A generic illuminating device for a vehicle is known from EP-A-0 390 208. According thereto, a light distribution of clear and blurred light is achieved. This light distribution, however, results from the use of a reflector. It is the object of the present invention to improve the illuminating device for a vehicle according to the preamble of claim 1. According to the invention, this object is achieved by an illuminating device for a vehicle having the features of claim 1. Advantageous further developments are set out in the dependent claims. The illuminating device provides a clear edge in the vertical direction of the light distribution and dispersion at the edge in the horizontal direction. According to the the present invention, a lens for a light distribution has a light incident surface and a light exit surface, where the exit surface is formed in an aspheric surface so that an aberration in the horizontal direction can be larger than an aberration in the vertical direction of the exit surface. Among light distributions formed by an outgoing light emitted from the exit surface, a peripheral portion in the horizontal direction is blurrier than a peripheral portion in the vertical direction. A radius of curvature of the outer periphery of a horizontal cross-section of the aspheric lens surface is formed smaller than a radius of curvature of the outer periphery of a vertical cross-section. Preferably, in order to form the radius of curvature of the outer periphery of the horizontal cross-section of the aspheric lens surface smaller than the radius of curvature of the outer periphery of the vertical cross-section, aspheric lens surface is made of a curved surface formed by combining ellipsoids, and the outer periphery of the vertical cross-section of the same lens surface is formed in an ellipsoid. Preferably, the lens for the light distribution has a total reflective surface inclined by a predetermined angle with respect to the vertical surface of the light axis, and the light distribution formed by the outgoing light from the exit surface is formed to be located slantingly in the vertical direction of the light axis based on the reflection by a total reflective surface. More preferably, the total reflective surface is formed to stray off the light-axis direction gradually as it goes closer to the exit surface, and also the inclining angle is formed to be gradually smaller as it goes closer to the exit surface. Thus, with the dispersion of light in the horizontal direction (x-axis direction) of the lens being larger than dispersion of light in the vertical direction (y-axis direction) of the lens, a blurred light distribution in the right and left peripheries can be obtained. Accordingly, in case a road surface is irradiated with a headlamp for a vehicle by using the illuminating device constructed as above, the boundary of bright and dark portions at the upper edge can be clear and the boundary of bright and dark portions can have a blurred light distribution, dispersing widely enough in the right and left directions. Thus, conditions required to an illuminating device for a vehicle, to emit a light as far as possible and as bright as possible without causing glaring against the on-coming vehicles on the opposite lane, and more importantly to emit the light brighter to pedestrians, can be satisfied. Other features and advantages of the present invention will become more apparent from the following detailed description when read with reference to the accompanying drawings, in which: FIGS. 1(a) to 1(c) are schematic views of a principle of the present invention; FIG. 2 is a perspective view showing a main portion of a lens for a hot zone light distribution of a first embodiment of the present invention; FIG. 3 is a vectorial view showing an aberration of the lens for the hot zone light distribution of FIG. 2; FIGS. 4(a) and 4(b) are perspective views showing an example where the lens for the hot zone light distribution of FIG. 2 is applied to a headlamp for a vehicle; FIG. 5 is a perspective view showing a first modification of the first embodiment of the present invention; FIG. 6 is a view showing a graph for explanation of the first modification of FIG. 5; FIGS. 7(a) to 7(d) are schematic views showing a second modification of the first embodiment of the present invention; FIGS. 8(a) and 8(b) are schematic views showing a second embodiment of the present invention; FIGS. 9(a1) to 9(c2) are schematic views explaining the second embodiment of the present invention; FIGS. 10(a) and 10(b) are perspective views showing a third embodiment of the present invention; and FIGS. 11(a) to 11(b) are perspective views showing a fourth embodiment of the present invention. Preferred embodiments of the present invention are described below with reference to the accompanying drawings. In FIGS. 1(a) to 1(c) showing the principle of the present invention, where a light-axis of a lens 10 as shown in FIG. 1(a) is a z-axis, a horizontal direction of the lens 10 is an x-axis, and a vertical direction of the lens 10 is a y-axis, and light is designed to be emitted from a focal position f of this lens 10. Here, as far as an outgoing light of a vertical cross-section of this lens 10 is concerned, a cross-sectional shape in the vertical direction is so designed as to make a beam emitted from the lens 10 substantially a parallel beam as shown in FIG. 1(b), that is, as to make an aberration at an infinite-point (this aberration means that a light emitted from one point does not converge on one point) substantially zero, on the other hand, an outgoing light of the horizontal cross-section of this lens 10 is so designed that a beam emitted from the lens 10 as shown in FIG. 1(c) cannot become a parallel beam, that is, a cross-sectional shape in the horizontal direction is so designed that an aberration at the infinite-point becomes larger than the aberration of the vertical cross-section. It has been found that a light does not diffuse in the vertical direction (y-axis), however, a light diffuses widely and flatly in the horizontal (x-axis) direction and also forms a blurred light distribution at the right and left peripheral edge portions if a converged light by a luminous body or a reflector or the like is disposed in the vicinity of the focal position f to irradiate the light in the z-axis direction ahead of the lens surface of the lens 10. Here, the lens 10 is not limited in a one-sided convex lens as shown in FIG. 1(a), but also it can be formed by combining biconvex lenses or concave-convex lenses. The embodiments of the present invention are explained next. (First Embodiment) FIG. 2 shows a perspective view showing a lens of the first embodiment. In FIG. 2, the lens 10 according to the present first embodiment is shaped like a roughly one quarter (1/4) of a cone, made of material having excellent light transmittance, for example, polycarbonate or acrylic resin material. This lens 10 is composed of a light incident surface 11 where a light flux emitted from a light source not shown in the figure enters in the z-axis direction (a light-axis), a light exit surface 12 forming a lens surface of an aspheric surface described below, a side total reflective surface 13 in the vertical direction with respect to the light-axis, and an upper total reflective surface 14 in the horizontal direction with respect to the light-axis. Here, a vertical cross-sectional (z - y plane) outer periphery A of the exit surface 12 is shaped like a lens having a focal point in the vicinity of a crossing point 13a between the incident surface 11 and the z-axis. Furthermore, a horizontal cross-sectional (z - x plane) outer periphery B has a focal point in the vicinity of a crossing point 13a between the incident surface 11 and the z-axis, however, the shape of the lens has a larger aberration than the vertical cross-sectional (z - y plane) outer periphery A. The horizontal cross-sectional (z - x plane) outer periphery B is a curved surface shifting gradually along the y-axis of the vertical cross-sectional (z - y plane) outer periphery A, while the vertical cross-sectional (z - y plane) outer periphery A is a curved surface shifting gradually along the x-axis of the horizontal cross-sectional (z - x plane) outer periphery B. Specifically, if a radius of curvature of the horizontal cross-sectional (z - x plane) outer periphery B is made smaller than a radius of curvature of the vertical cross-sectional (z - y plane) outer periphery A, the direction and the size of the aberration is in a state shown in FIG. 3. FIG. 3 is a view where the aberration of the beam seen from the incident direction (z-axis direction) of a light of the exit surface 12 is indicated in vectors (arrow marks in the figure). From FIG. 3, it is understood that the aberration of the lens 10 becomes larger in the horizontal direction (x-axis direction), the aberration conversely becomes smaller as it goes closer to the vertical direction (y-axis direction). Therefore, the light distribution does not disperse widely in the vertical direction (y-axis direction) in order not to cause glaring against the on-coming vehicles running on the opposite lane, however it disperses widely in the horizontal direction (x-axis direction) which causes a blurred light distribution at the peripheral portions. Thus, light intensity in the horizontal direction (x-axis direction) so smoothly decreases that uneven distribution of light which may be caused by a sudden change of the light intensity can be prevented. Hereinafter, an example which adopts the above-described lens 10 to a low beam of a headlamp for a vehicle is explained. FIGS. 4(a) and 4(b) are views showing an example which adopts the 10 to a low beam of a headlamp for a vehicle. In FIG. 4(a) showing a headlamp for a vehicle, the headlamp comprises an optical fiber 30 emitting a light by entering the light generated by an electrically-driven light source not shown in the figure, a lens 20 for a flat light distribution forming a flat light distribution 41 (a light distribution made of a very widely area dispersing right and left below the horizontal-axis H - H of FIG. 4(b)) by entering the light transmitted through this optical fiber 30, and the lens 10 for hot zone light distribution forming a hot zone light distribution 42. As shown in FIG. 4(b), a light distribution overlapping near the center of the flat light distribution and illuminating far away of the vehicle. Moreover, FIG. 4(b) shows a light distribution 40 formed by the light irradiated by the lens 20 for the flat distribution and the lens 10 for the hot zone light distribution. The lens 20 for the flat light distribution made of such a material having excellent light transmittance as a polycarbonate or acrylic resin material is substantially formed in the shape of a fan. This lens 20 for the flat light distribution comprises an incident surface 21 partially glued with a transparent adhesive via a shade 32 at the upper portion of the exit surface 31 of the optical fiber 30, an exit surface 22 forming a biconvex lens for upper and lower portions, left and right side surfaces 23, 24 forming reflective surfaces, respectively, and a bottom surface 25 forming the same reflective surface. The focal point of this lens 20 for the flat light distribution is designed to be placed in the vicinity of the incident surface 21. The lens 10 for the hot zone light distribution comprises an incident surface 11 partially glued with a transparent adhesive via a shade 33 at the lower portion of the optical fiber 30, an exit surface 12 forming the direction and the size of the aberration as shown in FIG. 3 by making a radius of curvature of the horizontal cross-sectional (z - x plane) outer periphery B smaller than a radius of curvature of the vertical cross-sectional (z - y plane) outer periphery A as shown in FIG. 2, a side total reflective surface 13 forming an inclined surface inclining in the clockwise direction by 7.5° with respect to the vertical surface along the irradiating direction, and another upper total reflective surface 14 forming a horizontal surface. It is to be understood that the incident surfaces 11 and 21 may be disposed as closely as possible to the optical fiber 30 without using adhesives. The upper total reflective surface 14 is adjacent to the side total reflective surface 13 as a boundary of a line c along the irradiating direction at the upper edge of the side total reflective surface 13. The shade 33 has a cut line 34 inclining by a predetermined angle (for example, 15° ) to the lower right toward irradiating direction, with respect to the horizontal surface. In addition, the focal position F of the lens surface in the vertical direction of the exit surface 12 is placed near the incident surface 11, and is designed to be positioned at a crossing point between the side total reflective surface 13 and the cut line 34 of the shade 33. Furthermore, the focal position of the lens surface in the horizontal direction of the exit surface 12 is set near the focal position F of the lens surface in the vertical direction. In the light distribution 40, as for some incident light entering the incident surface 11 of the lens 10 for the hot zone light distribution from the optical fiber 30, the hot zone light distribution 42 has an area 42a formed by a direct light emitted from the direct exit surface 12 without reflecting on the side total reflective surface 13 and the upper total reflective surface 14 and an area 42a z dispersing blurredly due to the aberration. Because the cut line 34 of the shade 33 inclines based on the focal position F of the exit surface 12 by a predetermined angle (for example, 15° ) to the lower right toward irradiating direction, these areas 42a and 42a z have the upper edge a inclining to the upper left by 15° from the horizontal axis H - H as shown in FIG. 4(b). Furthermore, the hot zone light distribution 42 has an area 42b formed by a reflected light emitted from the exit surface 12 after reflecting on the side total reflective surface 13 and an area 42b z dispersing blurredly due to the aberration. Based on the focal position F of the exit surface 12, as shown in FIG. 4(b), these areas 42b and 42b z are positioned having a substantially horizontal upper edge b immediately below the horizontal axis H - H. In addition, the hot zone light distribution 42 has an area 42c formed by a reflected light emitted from the exit surface 12 after reflecting on the upper total reflective surface 14 and an area 42c z dispersing blurredly due to the aberration. Moreover, it has an area 42d formed by a re-reflected light emitted from the exit surface 12 after reflecting on the side total reflective surface 13 again, posterior to reflecting on the upper total reflective surface 14 and an area 42d z dispersing blurredly due to the aberration. These areas 42c, 42c z , 42d, and 42d z are formed, based on the focal position F of the exit surface 12, as shown in FIG. 4 (b), immediately below the respective areas 42a and 42a z , and immediately below the respective areas 42b and 42b z . Here, in the hot zone light distribution 42, an additional area also exists which is formed by a re-reflected light emitted from the exit surface 12 after reflecting on the upper total reflective surface 14 again, posterior to reflecting on the side total reflective surface 13, however, the intensity of illumination of this area is so low that its illustration is omitted. Furthermore, in case a headlamp of an illuminating device for a vehicle of the present embodiment is used, although laws, regulations or the like generally reqires a vehicle to run on either the right lane or the left lane, the hot zone light distribution illuminating a far distant area without causing glaring against the on-coming vehicle can be obtained whether it is the right or the left traffic system by positioning the areas 42a and 42a z located at the upper side to the left side in case of a vehicle running on the left lane and by positioning the same areas to the right side in case of a vehicle running on the right lane. In this instance, as far as a reflective surface (the side total reflective surface 13 in case of FIG. 4(a)) in the vertical direction is concerned, it should be disposed, inclining to the left side for a vehicle running on the left lane and to the right side for a vehicle running on the right side lane from the incident surface of the lens 10 for the hot zone light distribution. (First Modification) The closer the aberration in the vertical direction (z - y plane) of the exit surface 12 of the lens 10 for the hot zone light distribution becomes to zero, it does not cause glaring against the on-coming vehicles running on the opposite lane, therefore, it is considered that the shape of the lens surface of the exit surface 12 to make the aberration in the vertical direction (z - y plane) to substantially zero in the present first modified embodiment. As a result, in order to make the aberration in the vertical direction (z - y plane) to substantially zero, it is desirable for the shape of the lens surface of the exit surface 12 to be a curved surface composed of a combination of elliptical-shaped lens surface of the exit surface 12. FIG. 5 is a view showing a lens 10a for a hot zone light distribution shaped like a curved surface composed of a combination of elliptical-shaped lens surface of the exit surface. In FIG. 5, when the longer diameter of the outer peripheral ellipsoid C of the vertical cross-section (z - y plane) of the lens 10a for the hot zone light distribution is a, the shorter diameter is b 0 , and the original points of the x-axis, the y-axis, and the z-axis are taken at the vertex of the lens 10a for the hot zone light distribution, the outer peripheral ellipsoid C of the vertical cross-section (z - y plane) is expressed by the following equation 3. [Equation 3] y 2 / b 0 2 + (z + a) 2 / a 2 = 1 Further, when the longer diameter of the outer peripheral ellipsoid D of the horizontal cross-section (z - x plane) is a, and the shorter diameter is b 1 , the outer peripheral ellipsoid D of the horizontal cross-section (z - x plane) is expressed in the following equation 4. [Equation 4] x 2 / b 1 2 + (z + a) 2 / a 2 = 1 Here, if the shorter diameter b 0 of the outer peripheral ellipsoid C of the vertical cross-section is larger than the shorter diameter b 1 of the outer peripheral ellipsoid D of the horizontal cross-section (b 0 > b 1 ), radius of curvature of the outer peripheral ellipsoid D of the horizontal cross-section becomes smaller than radius of curvature of the outer peripheral ellipsoid C of the vertical cross-section, thus, the aberration shown in FIG. 3 is provided. In this case, when the shorter diameter of the outer peripheral ellipsoid E of a cross-section in a surface inclining by ° from the y-axis is b 2 , and if this shorter diameter b 2 is changed continuously from b 0 to b 1 with respect to , the aberration is not apt to occur in the vertical direction, so that a light distribution disperses owing to its aberration in the horizontal direction and does not cause glaring against the on-coming vehicles on the opposite lane. In order to change b 2 continuously from b 0 to b 1 with respect to , for example, as shown with a curved line (a) in FIG. 6, the shorter diameter b 2 has to be linearly changed from b 0 to b 1 as  becomes closer to π / 2 (x-axis) from zero (y-axis), or as shown with a curved line (b) of FIG. 6, the shorter diameter b 2 has to be non-linearly changed from b 0 to b 1 as  becomes closer to π / 2 (x-axis) from zero (y-axis), or as shown with a curved line (c) in FIG. 6, when  is between zero (y-axis) and nearby π / 2 (x-axis), the shorter diameter b 2 should be left as b 0 , however, the shorter diameter b 2 should be abruptly changed to b 1 between nearby π / 2 (x-axis) and π / 2 (x-axis). In this case, as shown with the curved line (c) in FIG. 6, when the shorter diameter b 2 is abruptly changed to b 1 between nearby π / 2 (x-axis) and π / 2 (x-axis), the aberration is not apt to occur furthermore in the vertical direction, which prevents glaring against the on-coming vehicles running on the opposite lane. Moreover, in the first modified embodiment, although the size of the aberration is adjusted by changing the shorter diameters of the outer peripheral ellipsoids of the vertical cross-section and the horizontal cross-section of the lens 10a for the hot zone light distribution, the size of the aberration can be adjusted by changing the longer diameter, or the size of the aberration can be adjusted by changing both the longer and shorter diameters at the same time. Furthermore, the lens surface of the exit surface is in the shape of an ellipsoid in order to adjust the aberration, however, it may be able to be shaped in a curved surface other than an ellipsoidal shape. (Second Modification) In the lens 10, 10a for the hot zone light distribution of the first embodiment and the first modification, it is substantially shaped like one quarter (1/4) of a cone, and also the side total reflective surfaces 13 and 13a are disposed inclining to the left side with respect to the light-axis direction (z-axis direction) by 7.5°, accordingly, the aberration direction is primarily in the left to upper left direction, which inclines the hot zone light distribution toward the left (FIGS. 4(a) and 4(b)). In order to compensate this, in the present second modified embodiment, a modification is performed on the total reflective surface of a side surface as shown in FIGS. 7(a) and 7(b). FIG. 7(a) is a view showing light distribution characteristics when a side total reflective surface of a lens 10b for hot zone light distribution is modified. On the other hand, FIG. 7(b) shows a perspective view of the lens 10b for the hot zone light distribution taken from the above, FIG. 7(c) shows a shape of an incident surface 11b of the lens 10b for hot zone light distribution, and FIG. 7(d) is a view showing a cross-sectional shape taken along the line 7(d) - 7(d) in FIG. 7(b). In case of a vehicle for running on the left side, to improve visibility at the footpath side, as shown in FIG. 7(a), it is required to incline it toward upper left by 15° from the horizontal-axis H - H. For that purpose, the side total reflective surface 13b of the lens 10b for the hot zone light distribution has, as shown with a two-dot line in FIG. 7(c) and FIG. 7(b) and FIG. 7(d), an inclined surface 13b 1 inclining toward the left side by 7.5° with respect to the vertical surface along the irradiating direction, and a cut line 34b of a shade 33b also inclines toward the lower right by 15° along the irradiating direction. When the inclined surface 13b 1 is disposed, similarly to the above-described first embodiment, the light distribution characteristic, as shown in FIG. 7(a), has an area formed by direct light 42a 1 , an area 42b 1 (inside of the two-dot line of FIG. 7(a)) formed by the reflective light on the inclined surface 13b 1 , an area 42c 1 formed by the reflective light on an upper total reflective surface 14b, and an area 42d 1 (inside of the two-dot line of FIG. 7(a)) formed by re-reflected light, i.e., the reflective light on the upper surface reflective surface 14b reflected again on the inclined surface 13b 1 . In FIG. 7(a), there is an area dispersing blurredly due to the aberration of the lens 10b for the hot zone light distribution as shown in FIG. 4(b), however, its illustration is omitted in this case. Here, as shown with broken lines of FIG. 7(b) and FIG. 7(d), by making a portion of the inclined surface 13b 1 an inclined surface 13b 2 inclining toward the x-axis positive direction, the right edge portion of the hot zone light distribution can be extended in the right direction, however, as shown with a broken line of FIG. 7(a), it is extended to the lower right side (areas 42b 2 and 42d 2 inside a broken line of FIG. 7 (a)) owing to the aberration of the lens 10b for the hot zone light distribution, so that visibility of a distant area at the right side decreases. To compensate this, as shown with a solid line of FIG. 7(b) and FIG. 7(d), by making a portion of the inclined surface 13b 2 an inclined surface 13b 2 awry toward the x-axis positive direction, as shown with a solid line of FIG. 7(a), the extended portion to the lower right side of the right edge portion of the hot zone light distribution can be compensated to the upper side (areas 42b 3 and 42d 3 inside a solid line of FIG. 7(a)). By making such a compensation, as shown in FIG. 7(d), the inclined surface 13b 3 of the cross-section F - F becomes an inclined surface of 4.5°, thus a smooth surface can be continuously formed between a point Z 1 at the incident side of the light of the inclined surface 13b 3 and a point Z 2 at the exit side. Furthermore, the surface between the point Z 1 at the incident side and the point Z 2 at the exit side can be formed in plural surfaces, or may be formed in a curved surface. Furthermore, in the second modified embodiment, similarly to the case of the first embodiment, in case a headlamp of an illuminating device for a vehicle of the present second modified embodiment is used, the hot zone light distribution illuminating a far distant area without causing glaring against the on-coming vehicle can be obtained whether it is the right or the left traffic system by positioning the area 42a 1 located at the upper side to the left side in case of a vehicle running on the left lane and by positioning the same area to the right side in case of a vehicle running on the right lane. In this case, as far as a reflective surface (the inclined surface 13b 3 in case of FIG. 7(d)) in the vertical direction is concerned, it should be disposed inclining to the left side for a vehicle running on the left lane and to the right side for a vehicle running on the right lane from the incident surface of the lens 10b for the hot zone light distribution. (Second Embodiment) In the first embodiment and its modified embodiments, although explanations have been made for a lens substantially shaped like one quarter (1/4) of a cone used for a lens for hot zone light distribution, two lenses substantially shaped like one quarter (1/4) of a cone can be combined to make them one lens substantially shaped like one half (1/2) of a cone, so that it can be a lens for hot zone light distribution. In FIG. 8(a), two lenses substantially shaped like one quarter (1/4) of a cone are combined to make a lens substantially shaped like one half (1/2) of a cone. This lens may be used for hot zone light distribution applied to low beam of a head lamp for a vehicle. The present second embodiment, in order to make the lens in the shape of a substantially one half (1/2) of a cone, comprises the lens 10b for the hot zone light distribution as in the foregoing embodiments and an additional lens 10c for hot zone light distribution having a total reflective surface vertically disposed with respect to the light-axis at a side surface. FIG. 8(a) illustrates a headlamp for a vehicle, whose headlamp comprises the optical fiber 30 emitting a light by entering the light generated by a light source not shown in the figure, the lens 20 for flat light distribution forming the flat light distribution 41 by entering the light transmitted through this optical fiber 30, the lens 10b for the hot zone light distribution forming a hot zone light distribution, and another lens 10c for the hot zone light distribution. Moreover, FIG. 8(b) shows a light distribution 40A formed by the light irradiated by the lens 20 for the flat distribution, the lens 10 for the hot zone light distribution and another lens 10c for the hot zone light distribution. In FIGS. 8(a) and 8(b), since the lens 20 for the flat light distribution, the optical fiber 30, the shades 32, 33 and the flat light distribution 41 are respectively the same as the lens 20 for the flat light distribution, the optical fiber 30, the shades 32, 33 and the flat light distribution 41 in the first embodiment of FIG. 4, explanations therefor are omitted. Also, in FIGS. 8(a) and 8(b), since the lens 10b for the hot zone light distribution and hot zone light distributions 43a 1 , 43b 3 , 43c 1 , and 43d 3 are respectively the same as the lens 10b for the hot zone light distribution and the hot zone light distributions 42a 1 , 42b 3 , 42c 1 , and 42d 3 of FIG. 7, explanations therefor are omitted. Furthermore, similarly to the hot zone light distributions 42a z , 42b z , 42c z , and 42d z of FIG. 4, the respective hot zone light distributions 43a 1z , 43b 3z , 43c 1z , and 43d 3z of FIG. 8(b) show areas of the peripheries of respective hot zone distributions 42a 1 , 42b 3 , 42c 1 , and 42d 3 dispersing blurredly owing to the aberration. Because the lens 10c for the hot zone light distribution shown in FIG. 8(a) has a side total reflective surface 13c vertically disposed with respect to the light-axis at the side surface, as shown in FIG. 8(b), the hot distribution 50 has an area 50a formed by a direct light emitted from the direct exit surface 12c without being reflected on the side total reflective surface 13c and the upper total reflective surface 14c. Since the cut line 34 of the shade 33 inclines, based on the focal position of the exit surface 12c, by a predetermined angle (for example, 15° ) to the lower right toward irradiating direction, this area has an upper edge c inclining to the upper left by 15° from the horizontal-axis H - H as shown in Fig. 8(b). Furthermore, the hot zone light distribution 50 has an area 50b formed by a reflected light emitted from an exit surface 12c after reflecting on a side total reflective surface 13c. Based on the focal position of the exit surface 12c, as shown in FIG. 8(b), this area 50b is positioned to have a substantially horizontal upper edge d immediately below the horizontal-axis H - H. In addition, the hot zone light distribution 50 has an area 50c formed by a reflected light emitted from the exit surface 12c after being reflected on the upper total reflective surface 14c. Moreover, it has an area 50d formed by a re-reflected light emitted from the exit surface 12c after being reflected on the side total reflective surface 13c again, posterior to reflecting on the upper total reflective surface 14c. These areas 50c and 50d are respectively formed, based on the focal position of the exit surface 12c, as shown in FIG. 8(b), immediately below the respective areas 50a and 50b. FIGS. 9(a1) to 9(c2) is a view showing a difference in the characteristics of each hot zone light distribution between the case where one lens substantially shaped like a quarter (1/4) of a cone is employed as a lens for the hot zone light distribution and the case where one lens substantially shaped like one half (1/2) of a cone by combining two lenses substantially shaped like a quarter (1/4) of a cone. In more detail, FIG. 9(a2) shows the shapes of the incident surface 11b of the lens 10b for the hot zone light distribution and the shade 33 of FIG. 7(b), while FIG. 9(a2) shows a characteristic of the hot zone light distribution. FIG. 9(b2) shows the shapes of the incident surfaces 11b and 11c of the lenses 10b and 10c for the hot zone light distribution, and the shade 33 of FIG. 8(a), and FIG. 9(b1) shows the same characteristic of the hot zone light distribution as in FIG. 8(b). FIG. 9(c2) shows the shapes of the incident surfaces of the lenses 10b and 10c for the hot zone light distribution, and the shade 33 of FIG. 8(b), and FIG. 9 (c1) shows a characteristic of the hot zone light distribution. As obvious from FIGS. 9(a1) to 9(c2), by additionally providing the lens 10c for the hot zone light distribution, in addition to the hot zone light distributions 42a 1 , 42b 3 , 42c 1 , and 42d 3 which can illuminate a distant area without causing glaring against the on-coming vehicles running on the opposite lane, it is possible to form a second hot zone light distribution 50 or 51 enabling to illuminate a desired targeted place in a distant area. In this case, by adding the lens 10c for the hot zone light distribution, an incident light (referred to a shaded portion (α in FIG. 9(a2)) which cannot be used when only using the lens 10b for the hot zone light distribution can be used, thus, usage efficiency of a light is improved. Moreover, The second hot zone light distribution 50 can irradiate the upper left portion in a distant area, by making the shape of the shade 33 as shown in FIG. 9(b2), and also can irradiate the center portion in a distant area, by making the shape of the shade 33 as shown in FIG. 9(c2). In the present second embodiment, although an explanation has been made based on the case of disposing the lens 10b for the hot zone light distribution at the left side in the light irradiating direction and disposing the lens 10c for the hot zone light distribution at the right side in the light irradiating direction, the right and left positions of these lenses 10b and 10c for the respective hot zone light distributions may be reversed. Furthermore, similarly to the first embodiment, the present second embodiment has been explained in case the illuminating device for a vehicle of the present second embodiment is used as a headlamp for a vehicle running on the left lane, however, in case it is used as a headlamp for a vehicle running on the right lane, the lenses 10b and 10c for the hot zone light distribution, and the shade 33 or shade 33a should be used by disposing them symmetrically. (Third Embodiment) Hereinafter, the third embodiment of the present invention is explained based on FIGS. 10(a) and 10(b). Fig. 10(a) is a perspective view showing a headlamp for a vehicle employing a lens substantially shaped like one half (1/2) of a cone of the present third embodiment as the hot zone light distribution as well as a view showing a characteristic of the light distribution. In FIG. 10(a), a headlamp for a vehicle comprising the optical fiber 30 emitting a light by entering the light generated by a light source not shown in the figure, the lens 20 for the flat light distribution forming the flat light distribution 41 by entering the light transmitted through this optical fiber 30, and the lens 10d for the hot zone light distribution in the shape of a substantially one half (1/2) of a cone forming a hot zone light distribution 60. In addition, FIG. 10(b) shows a light distribution 40B formed by a light irradiated by the lens for the flat light distribution 20 and the lens 10d for the hot zone light distribution 10d. In FIG. 10(a) and FIG. 10(b), because the lens 20 for the flat light distribution, the optical fiber 30, the shades 32, 33, and the flat light distribution 41 are respectively the same as the lens 20 for the flat light distribution, the optical fiber 30, the shades 32, 33, and the flat light distribution 41 of the first embodiment of FIG. 4(a), an explanation therefor is omitted. A vertical cross-section (z - y plane) of an exit surface 12d of the lens 10d for the hot zone light distribution of the present third embodiment has a focal point in the vicinity of an incident surface 11d and the lens surface has a radius of curvature to be substantially zero aberration. Furthermore, as for the lens surface, a radius of curvature of the horizontal cross-section (z - x plane) of the exit surface 12d of the lens 10d for the hot zone light distribution is made smaller than a radius of curvature of the vertical cross-section (z - y plane). That is, the aberration of the horizontal cross-section (z - x plane) is formed larger than the aberration of the vertical cross-section (z - y plane). Accordingly, a light emitted from the exit surface 12d of the lens 10d for the hot zone light distribution disperses in the right and left directions, and also can form a hot zone light distribution 60 enabling to illuminate a far distant area without causing glaring against the on-coming vehicles running on the opposite lane. The hot zone light distribution 60 shown in FIG. 10(b) has an area 60a formed by a direct light emitted from a direct exit surface 12d without reflecting on the upper total reflective surface 14d, an area 60a z where the periphery of the area 60a disperses blurredly due to the aberration, an area 60b formed by a reflective light emitted from an exit surface 12d after reflecting on the upper total reflective surface 14d, and an area 60b z where the periphery of the area 60b disperses blurredly due to the aberration. In the present third embodiment, because the aberration of the horizontal cross-section (x-axis direction) is formed larger than the aberration of the vertical cross-section (y-axis direction), a light emitted from the exit surface 12d of the lens 10d for the hot zone light distribution disperses in the right and left direction, and also can form a hot zone light distribution 60 enabling to illuminate a far distant area without causing glaring against the on-coming vehicles running on the opposite lane. Besides, in the third embodiment, although the lens 20 for the flat light distribution forming the flat light distribution 41 and the lens 10d for the hot zone light distribution in the shape of a substantially one half (1/2) of a cone forming the hot zone light distribution 60 are composed by disposing them vertically, the positions of these lens 20 for the flat light distribution and the lens 10d for the hot zone light distribution 10d can be reversed in the construction. (Fourth Embodiment) In the embodiment, an explanation has been made based on an example which is constructed by disposing the lens 20 for the flat light distribution forming the flat light distribution and the lens 10d for the hot zone light distribution in the shape of a substantially one half (1/2) of a cone forming the hot zone light distribution 60 vertically, however, the lens for the flat light distribution and the lens for the hot zone light distribution in the shape of a substantially one half (1/2) of a cone can be disposed horizontally in the construction. Hereinafter, the fourth embodiment of the present invention is explained based on FIGS. 11(a) and 11(b). FIG. 11(a) is a perspective view showing the present fourth embodiment where the lens for the flat light distribution forming the flat light distribution is disposed at the left side in the light-axis direction (z-axis direction) and the lens for the hot zone light distribution using a lens in the shape of a substantially one half (1/2) of a cone is disposed at the right side of the light-axis direction (z-axis direction), and FIG. 11(b) is a view showing a characteristic of the light distribution. FIG. 11(a) shows a headlamp for a vehicle comprising an optical fiber 30a emitting a light by entering the light generated by a light source not shown in the figure, a lens 20a for the flat light distribution emitting and forming the flat light distribution 42 by entering the light transmitted through this optical fiber 30a, an optical fiber 30b emitting a light by entering the light generated by a light source not shown in the figure, and the lens 10e for the hot zone light distribution in the shape of a substantially one half (1/2) of a cone emitting and forming a hot zone light distribution by entering the light emitted by this optical fiber 30b. In addition, FIG. 11(b) shows a light distribution 40c formed by a light irradiated by the lens 20a for the flat light distribution and the lens for the hot zone light distribution 10e. A vertical cross-section (z - y plane) of an exit surface 12e of the lens 10e for the hot zone light distribution of the present fourth embodiment has a focal point in the vicinity of an incident surface 11e and the lens surface has a radius of curvature to be substantially zero aberration. Furthermore, as for the lens surface, a radius of curvature of the horizontal cross-section (z - x plane) of the exit surface 12e of the lens 10e for the hot zone light distribution is made smaller than a radius of curvature of the vertical cross-section (z - y plane). That is, the aberration of the horizontal cross-section (z - x plane) is formed larger than the aberration of the vertical cross-section (z - y plane). Moreover, at the side surface, a side total reflective surface 13e forming an inclined surface inclining clockwise by 7.5° with respect to the vertical surface along the irradiating direction is formed. Accordingly, a light emitted from the exit surface 12e of the lens 10e for the hot zone light distribution can form a hot zone light distribution 70 enabling to illuminate an upper left place in a distant area without causing glaring against the on-coming vehicles running on the opposite lane. A hot zone light distribution 70 shown in FIG. 11(b) has an area 70a formed by a direct light emitted from a direct exit surface 12e without reflecting on the side total reflective surface 13e, an area 70a z where the periphery of the area 70a disperses blurredly due to the aberration, an area 70b formed by a light emitted from the exit surface 12e after reflecting on the side total reflective surface 13e, and an area 70b z where the periphery of the area 70b disperses blurredly due to the aberration. In the present fourth embodiment constructed as above, because the aberration of the horizontal cross-section (x-axis direction) is formed larger than the aberration of the vertical cross-section (y-axis direction), a light emitted from the exit surface 12e of the lens 10e for the hot zone light distribution disperses in the right and left direction, and also can form the hot zone light distribution 70 enabling to illuminate a far distant area without causing glaring against the on-coming vehicles running on the opposite lane. Besides, in the fourth embodiment, although an explanation has been made based on an example where the lens 20a for the flat light distribution is disposed at the left side of the light-axis direction (z-axis direction) and the lens 10e for the hot zone light distribution in the shape of a substantially one half (1/2) of a cone is disposed at the left side of the light-axis direction (z-axis direction), the right and left positions of these lens 20a for the flat light distribution and the lens 10e for the hot zone light distribution can be reversely disposed. In the fourth embodiment, the side surface forms the side total reflective surface 13e forming an inclined surface inclining clockwise by 7.5 ° with respect to the vertical surface along the irradiating direction, however, as for a vehicle running on the right lane, the side surface forms the side total reflective surface forming an inclined surface inclining counterclockwise by 7.5 ° with respect to the vertical surface along the irradiating direction. The present invention is not limited to the foregoing embodiments but may be modified in many other ways without departing from the scope of the invention defined in the appended claims.

Claims: An illuminating device for a vehicle comprising: a lens (10) having an incident surface (11) and an exit surface (12); wherein a light distribution of clear and blurred light is achieved characterized in that said lens (10) provides said light distribution; the exit surface is an aspheric lens surface so that an aberration in a horizontal direction (x) can be larger than an aberration in a vertical direction (y) of the exit surface; a peripheral portion in a horizontal direction is blurrier than a peripheral portion in a vertical direction among light distributions formed by an outgoing light emitted from the exit surface, and a radius of curvature of the outer periphery of the horizontal cross-section of the aspheric lens surface is formed smaller than a radius of the curvature of the outer periphery of the vertical cross-section. An illuminating device for a vehicle as set forth in claim 1, wherein: the aspheric lens surface is made of a curved surface formed by combining ellipsoids; the outer periphery of the vertical cross-section of the lens surface is formed in an ellipsoid expressed by y 2 / b 0 2 + (z + a) 2 / a 2 = 1, and the outer periphery of the horizontal cross-section of the lens surface is formed in an ellipsoid expressed by x 2 / b 1 2 + (z + a) 2 / a 2 = 1; and the lens surface is so formed as to make the shorter diameter b 0 of the outer peripheral ellipsoid of the vertical cross-section larger than the shorter diameter b 1 of the outer peripheral ellipsoid of the horizontal cross-section (b 0 > b 1 ), with a z-axis representing a light-axis, an x-axis representing a horizontal-axis and a y-axis representing a vertical-axis, respectively, and a representing the longer diameter of the outer peripheral ellipsoid of the vertical cross-section or the longer diameter of the outer peripheral ellipsoid of the horizontal cross-section. An illuminating device for a vehicle as set forth in claim 2, wherein: b 2 is designed to linearly decrease from b 0 to b 1 as  becomes from 0 degree to 90 degrees in case the longer diameter of the outer peripheral ellipsoid of the cross-section inclining by  degrees from the y-axis is a, and the shorter diameter is b 2 while having a relation of b 0 > b 2 > b 1 . An illuminating device for a vehicle as set forth in claim 2, wherein: b 2 is designed to non-linearly decrease from b 0 to b 1 as  becomes from 0 degree to 90 degrees in case the longer diameter of the outer peripheral ellipsoid of the cross-section inclined by  degrees from the y-axis is a, and the shorter diameter is b 2 while having a relation of b 0 > b 2 b> b 1 . An illuminating device for a vehicle as set forth in claim 4, wherein:  is left as b 0 when it is from 0 to nearby 90 degrees, and  is designed to be abruptly changed to b 1 when  is near 90 degrees, in case the longer diameter of the outer peripheral ellipsoid of the cross-section inclining by  degrees from the y-axis is a and the shorter diameter is b 2 while having a relation of b 0 > b 2 > b 1 . An illuminating device for a vehicle as set forth in claim 1, wherein: the lens for a light distribution has a total reflective surface (13) inclined by a predetermined angle with respect to the vertical surface of the light-axis; and the light distribution formed by the outgoing light emitted from the exit surface is formed to be located slantingly in the vertical direction of the light-axis based on the reflection by the total reflective surface. An illuminating device for a vehicle as set forth in claim 6, wherein: the light distribution located slantingly in the vertical direction of the light-axis has an upper edge increasing its height toward outside, and the inclining angle of the total reflective surface is approximately half of the inclining angle with respect to the horizontal surface of the upper edge. An illuminating device for a vehicle as set forth in claim 6, wherein: the total reflective surface is formed to stray off the light-axis direction gradually as it goes closer to the exit surface, and the inclining angle is formed to be gradually smaller as it goes closer to the exit surface. An illuminating device for a vehicle as set forth in claim 6, wherein: the total reflective surface is formed at the left side with respect to the light-axis in case of a vehicle running on the left lane but formed at the right side with respect to the light-axis in case of a vehicle running on the right lane. An illuminating device for a vehicle as set forth in claim 1, wherein said exit surface is: a curved surface (12) defined to have a first and a second focal points with respect to a first and second axes (y, x) orthogonal to each other, respectively; the first focal point being located substantially at the predetermined position; and the second focal point being deviated from the predetermined position, wherein a first outer edge of a projected light with respect to the first axis is formed more clearly than a second edge of the projected light with respect to the second axis. An illuminating device for a vehicle as set forth in claim 10, wherein: the first axis extends vertically and the second axis extends horizontally; and the first edge corresponds to a boundary of the projected light in a vertical direction and the second edge corresponds to a boundary of the projected light in a horizontal direction. An illuminating device for a vehicle as set forth in claim 10, further comprising: a light source for providing the light at the predetermined position; and a defining member located forward the light source to define a pattern of a light projected from the lens surface. An illuminating device for a vehicle as set forth in claim 10, wherein: a reflection surface (14) is provided to extend along the second axis; and the second edge of the projected light is defined by the reflection of light by the reflection surface. An illuminating device for a vehicle as set forth in claim 13, wherein: the reflection surface extends horizontally; and the second edge includes an upper and a lower edges one of which is defined by the reflection of light by the reflection surface. An illuminating device for a vehicle as set forth in claim 10, wherein: the curved surface is curved continuously in three dimensions. An illuminating device for a vehicle according to claim 1, wherein said exit surface (12) is a curved surface (12) defined by a horizontal curved line (B) and a vertical curved line (A) which are different from each other, the lens body passing a light therethrough to project the light forward to illuminate a predetermined area which covers an on-coming vehicle side; and wherein the curved surface in a horizontal direction (x) defines horizontal side edges, and in a vertical direction (y) defines an upper side edge of the projected light at the on-coming vehicle side more clearly than the horizontal side edges. An illuminating device for a vehicle as set forth in claim 16, wherein: the curved surface in the vertical direction defining a lower side edge of the projected light less clearly than the upper side edge by the light passing a light path different from a light path along which the light for defining the upper side edge passes.

Inventors: OKUCHI HIROAKI, OKUCHI, HIROAKI, Okuchi, Hiroaki, c/o Nippondenso Co., Ltd.
Applicants: DENSO CORP, DENSO CORPORATION
Application year: 1996
Main classification: F21V5
IPC codes: F21S8, F21V5