GB2314151A

GB2314151A - A license plate lamp with cover lens comprising both diffusion and plain lens portions

Info

Publication number: GB2314151A
Application number: GB9710989A
Authority: GB
Inventors: Masayoshi Unno
Original assignee: Koito Manufacturing Co Ltd
Current assignee: Koito Manufacturing Co Ltd
Priority date: 1996-06-06
Filing date: 1997-05-28
Publication date: 1997-12-17
Anticipated expiration: 2017-05-28
Also published as: GB9710989D0; CN1172037A; CN1133552C; JP3222383B2; GB2314151B; JPH09323587A

Abstract

A license plate lamp 10 comprising a light source 12 and a cover lens 14, said cover lens having a first part 14A formed from a diffusion lens portion located to illuminate the part 2A of the license plate 2 closest to said light source and the area below, and a second part formed 14B from a plain lens portion through which light beams are directed to illuminate those parts 2B of the license plate located farthest from said light source and the area above. In this way, uniform illumination of the license plate is achieved.

Description

VEHICLE LAMP The present invention relates to vehicle lamps, and more particularly to lens structure of a license plate lamp.

A license plate lamp is to irradiate a license plate mounted on the rear end of a vehicle. If the brightness of the license plate of a vehicle irradiated by the license plate lamp is fluctuated depending on the parts of the license plate, then it is rather difficult for, for instance, driver in a following vehicle to read the license plate.

Hence, the license plate lamp should irradiate the whole license plate as uniformly as possible.

On the other hand, in order that the license plate lamp may not obstruct a person's reading of the license plate, the license plate lamp is set near the periphery of the license plate. Accordingly, the part of the license plate which is close to the license plate lamp is bright, while the part of the license plate which is far from the lamp is dark.

In order to overcome the above-described difficulty, heretofore the following method has been proposed: An inner surface of the lens which covers the light source of the license plate lamp is frosted to diffuse output light of the light source, thereby to improve the distribution of brightness of the license plate.

However, the method has the following difficulty: That is, in the method, the whole inner surface of the lens is subjected to frosting. Therefore, the above-described phenomenon remains as it is that the part of the license plate which is close to the license plate lamp is bright, while the part of the license plate which is far from the lamp is dark. That is, with the method, it is difficult to make the license plate uniform in the distribution of brightness.

In view of the foregoing, the following method has been proposed: That is, the license plate lamp is disposed at a front of the license plate (rearward of the vehicle) to the extent that an allowable brightness distribution (the ratio of highest brightness to lowest brightness is 20 : 1 or less) is obtained. However, the method cannot be practical without elongating the front-to-rear length of the vehicle body as much, or reducing the trunk room or vehicle room space as much.

In view of the foregoing, an object of the invention is to provide a vehicle lamp which is free from the difficulty that the lamp must be set far behind the license plate, and which makes the license plate uniform in the distribution of brightness.

The foregoing object of the invention is achieved by a provision of a license plate lamp in which parts of the lens forming the lamp are different in the function of diffusion. Specifically, a vehicle lamp positioned near the periphery of a license plate to irradiate the license plate comprises a light source and a lens covering the light source. The lens is provided with a first part which is formed from a diffusion lens portion which locates near a straight line connecting the light source and a part of the license plate which is closest to the light source, and a second part which is formed from a plain lens portion which locates near straight lines connecting the light source and parts of the license plate which are farthest from the light source.

The 'diffusion lens portion" is not limited in diffusing structure nor in diffusing direction. That is, all that is necessary for the diffusion lens portion is the function of diffusion.

Generally, the part of a license plate which is closest to the light source (hereinafter referred to as "the closest part", when applicable) is intensively irradiated by the incident light from the light source, thus being high in brightness. On the other hand, the part of the license plate which is farthest from the light source (hereinafter referred to as "the farthest part", when applicable) is not intensively irradiated by the incident light from the light source, thus being low in brightness.

However, as was described above, in the vehicle lamp of the invention, the first part of the lens is a diffusion lens portion which locates near the straight line connecting the light source and the closest part of the license plate.

Hence, the bundle of incident light beams to the closest part of the license plate is reduced, so that the closest part is illuminated low in brightness. On the other hand, the second part of the lens is the plain lens portion which locates near straight lines connecting the light source and the farthest parts of the license plate. Hence, the bundle of light beams to the farthest part of the license plate is not reduced, and is maintained high in brightness. Thus, the whole area of the license plate is illuminated substantially uniform in the distribution of brightness.

Accordingly, with the vehicle lamp of the invention, in order to uniformly irradiate the license plate, it is unnecessary to position the license plate lamp far from the license plate.

As was described above, the structure of the diffusion lens portion is not limited. For example, the surface of the lens is subjected to frosting or graining treatment, or it is in the form of steps1 or those methods are suitably combined with one another to form the diffusion lens portion.

The above-described vehicle lamp should be positioned near the peripheral edge of the license plate; however, its position is not particularly limited. However, it is preferable that the lamp positions substantially at the middle of the upper peripheral edge of the license plate, and the diffusion lens portion which is in the form of steps diffuses the output light of the light source vertically, and the plain lens portions are formed on both right and left sides of the diffusion lens portion. In this case, merely a single license plate lamp can illuminate the whole license plate substantially uniformly in brightness.

In the accompanying drawings: FIG. 1 is a sectional side view showing a vehicle lamp, which constitutes a preferred embodiment of the invention; FIG. 2 is a view taken in the direction of the arrow Ii in FIG. 1; FIG. 3 is a sectional side view of the lens of the above-described vehicle lamp; FIG. 4 is a view taken in the direction of the arrow IV in FIG. 3; and FIG. 5 is a sectional side view showing a modified embodiment of the invention.

FIG. 1 is a sectional side view showing a vehicle lamp 10, embodying the invention, and FIG. 2 is a view taken in the direction of the arrow II in FIG. 1.

As shown in FIGS. 1 and 2, the vehicle lamp 10, the embodiment of the invention, is a license plate lamp adapted to illuminate a license plate 2 mounted at the rear end of a vehicle body. The lamp 10 positions rearward and obliquely upwardly of the middle of the upper edge of the license plate 2.

The license plate lamp 10 comprises: a light source (a wedge base bulb) 12 having a filament 12a which extends in a right-to-left direction (a direction of vehicle width); a lens 14 which is substantially semi-spherical and covers the light source 12; and a body 16 supporting the light source 12 and the lens 14 on a vehicle body member 4; and a pair of contacts 18.

FIG. 3 is a sectional side view of the abovedescribed lens 14, and FIG. 4 is a view taken in the direction of the arrow IV in FIG. 3.

As shown in FIGS. 3 and 4, the semi-spherical end portion of the lens 14 includes a diffusion lens portion 14A, and a pair of plain lens portions 14B (described later).

The diffusion lens portion 14A is made up of a first diffusion lens part 14A1, a second diffusion lens part 14A2, and a third diffusion lens part 14A3. The first diffusion lens part 14A1 corresponds to a region of the lens 14 which extends from the lowermost end point of the lens 14 near to the front part of the latter 14. The inner surface of the first diffusion lens part 14A1 is in the form of steps (six steps 14Ala), and is frosted. The six steps 14Ala forming the first diffusion lens part 14A1 are saw-tooth-shaped in section and extending in a right-to-left direction. Those lens steps 14Ala refracts the output light of the light source 12 vertically (upwardly and downwardly), and refracts the light vertically (upwardly and downwardly) as a whole which is applied to the first diffusion lens part 14A1 (cf.

FIG. 1). Since those lens steps 14Ala are frosted, the above-described vertical (upward and downward) diffusion light beams are transmission light beams which are scattered.

The second diffusion lens part 14A2 corresponds to a region of the lens 14 which is closer to the front part of the letter 14 than the first diffusion lens part 14A1. The second diffusion lens part 14A2 is formed by subjecting the inner surface of the lens 14 to graining treatment and then to frosting treatment. The light beams passing through the second diffusion lens part 14A2 is greatly scattered because, as was described above, the inner surface of the latter 14A2 has been subjected to graining and to frosting.

The third diffusion lens part 14A3 corresponds to a region of the lens 14 which locates slightly behind the lowermost end point of the lens 14, having an area which is the sum of the areas of the first and second diffusion lens parts 14A1 and 14A2. Similarly as in the case of the second diffusion lens part 14A2, the third diffusion lens part 14A2 is also formed by subjecting the inner surface of the lens 14 to graining and then to frosting treatments. Therefore, the light beams passing through the second diffusion lens part 14A3 are greatly scattered because, as was described above, the inner surface of the latter 14A3 has been subjected to graining and to frosting treatments.

The pair of plain portions 14B (mentioned above) are provided on the right and left sides of the aforementioned diffusion lens portion 14A. As is seen from FIG. 4, the diffusion lens portion 14A, and the plain portions 14B are bisymmetrical.

As shown in FIGS. 1 and 2, the first diffusion lens part 14A1 corresponds to the region locating near the straight line connecting the light source 12 and the middle 2A of the upper edge of the license plate 2 which is closest to the light source 12, and the peripheral region below the firstly mentioned region. The refracting powers of the six lens steps 14Ala forming the first diffusion lens part 14A1, are so determined that, as shown in FIG. 1, light is scarcely applied to the upper edge 2A. In this connection, refracted light beams are applied to the lower end portion of the middle (as viewed in the right-to-left direction) of the license plate 2 which (the lower end portion) is farthest from the light source 12.

On the other hand, the plain portions 14B, as shown in FIG. 2, corresponds to the regions which are near the straight lines connecting the light source 12 and both (right and left) ends 2B of the lower edge of the license plate 2 which (both ends) are farthest from the light source, and the region above the firstly mentioned regions, so that the light beams scarcely irradiate the two right and left ends 2B, and the area above those ends 2B.

The functions of the above-described embodiment will be described.

In the embodiment, the license plate lamp 10 is provided rearward and obliquely upwardly of the middle of the upper peripheral edge of the license plate 2. In this case, in general, the middle 2A of the upper edge portion of the license plate 2 is made high in illuminance by the incident light beams from the light source 12, thus being high in brightness. On the other hand, the two right and left ends 2B of the lower edge of the license plate are made low in illuminance by the incident light beams from the light source 12, thus being low in brightness.

In the embodiment, the first diffusion lens part 14A1 corresponds to the region which is located near the straight line connecting the light source 12 and the middle 2A of the upper edge of the license plate 2 which is closest to the light source 12, and the peripheral region below the firstly mentioned region. Therefore, the bundle of incident light beams to the middle 2A of the upper edge of the license plate may be reduced thereby to reduce the brightness of the middle 2A of the upper edge of the license plate 2. Furthermore, the refracting powers of the six lens steps 14Ala forming the first diffusion lens part 14A1 are so determined that light beams are scarcely applied to the middle 2A of the upper edge of the license plate 2, and that light beams are intensively applied to the lower end part of the middle portion (as viewed in the right-to-left direction) of the license plate 2 which (lower end part) is farthest from the light source 12.

Hence, the middle (as viewed in the right-to-left direction) of the license plate is illuminated uniformly in the distribution of brightness. The lens steps 14Ala are subjected to frosting, and therefore light beams passing through those lens steps 14Ala are scattered. This feature decreases the unevenness of the irradiating light beam which is caused because the inner surface of the lens 14 is in the form of steps.

In the embodiment, the plain lens portions 12B corresponds to the lens regions near the straight lines connecting the light source 12 and both right and left ends 2B of the lower edge of the license plate 2 and to the peripheral regions above them (the lens regions). Hence, the bundle of light beams applied to the right and left end portions including the both ends 2B of the lower edge is not decreased; that is, the right and left end portions can be maintained high in brightness.

In the lens 14, the second diffusion lens part 14A2, which is subjected to graining and frosting treatments, is formed near the front of the first diffusion lens part 14A1.

Hence, the part of the license plate is uniformly irradiated thereby which (part) is not sufficiently irradiated by the light beams passed through the first diffusion lens part 14A1 and the plain portions 12B.

In the above-described lens 14, the third diffusion lens part 14A3 does not contribute to the irradiation of the license plate 2. However, since the inner surface of the third diffusion lens part 14A3 is subjected to graining and frosting treatments, the light beams which passes through the third diffusion lens part 14A3 and scattered, can be utilized as light beams which indirectly illuminate the license plate 2.

As is apparent from the above description, in the embodiment, although the license plate lamp 10 is located near the license plate 2, the whole area of the license plate 2 is illuminated substantially uniformly in brightness distribution.

Furthermore, in the embodiment, it is unnecessary to position the lamp far behind the license plate 2 to irradiate the latter 2 uniformly in its entirety. In this connection, it should be noted that this effect is obtained by using only one license plate lamp 10.

However, it goes without saying that, depending on the configuration of the vehicle body and other conditions, more than one license plate lamp may be employed as shown in Fig. 5.

FIG. 5 shows two license plate lamps 10 which position near and obliquely backwardly of the middle parts of the right and left edges of the license plate 2. In the case where two right and left license plate lamps 10 are arranged in the above-described manner. The parts 2A' of the license plate 10 are closest to the two lamps 10, respectively, and the parts 2B' are farthest from the lamps 10, respectively.

The lens of each of the license plate lamps 10 has a pair of plain lens portions 14B'. Hence, the output light of the light source 12 is applied through those plain portions 14B' to the parts 2B'. In this case, the angle of irradiation to the middle parts 2B' of the upper and lower edges is smaller than the angle of irradiation to the parts 2B at both ends of the lower edge shown in FIG. 2. Therefore, it is desirable that each of the plain portions 14B' extends closer to the center of the lens 14 than each of the plain portion 14B shown in FIG. 2.

Claims

1. A vehicle lamp positioning near the periphery of a license plate of a vehicle to illuminate the license plate, the vehicle lamp comprising: a light source; and a cover lens covering said light source, said lens comprising: a first part formed from a diffusion lens portion locating near a straight line connecting said light source and a part of the license plate which is closest to said light source, and a second part formed from a plain lens portion locating near straight lines connecting said light source and parts of the license plate which are farthest from said light source.

2. The vehicle lamp as claimed in claim 1, wherein said first part of said cover lens is subjected to the frosting treatment.

3. The vehicle lamp as claimed in claim 1, wherein said first part of said cover lens is subjected to the graining treatment.

4. The vehicle lamp as claimed in claim 1, wherein said first part of said cover lens is formed with lens steps.

5. The vehicle lamp as claimed in claim 1, wherein said first part of said cover lens is formed by a combination of at least two of frosting treatment, graining treatment and lens steps.

6. The vehicle lamp as claimed in claim 1, wherein said diffusion lens portion is formed on an inner surface of said cover lens.

7. The vehicle lamp as claimed in claim 1, wherein said diffusion lens portion is formed on an outer surface of said cover lens.

8. The vehicle lamp as claimed in claim 1, wherein said diffusion lens portion of said cover lens comprises a first, second and third diffusion lens parts.

9. The vehicle lamp as claimed in claim 8, wherein said first diffusion lens part corresponds to a region of said cover lens extending from the lowermost end point of said cover lens near to the front part of the latter.

10. The vehicle lamp as claimed in claim 9, wherein said first diffusion lens part is in the form of more than one step, and is frosted.

11. The vehicle lamp as claimed in claim 8, wherein said second diffusion lens part corresponds to a region of said cover lens which is closer to the front part of the letter than said first diffusion lens part.

12. The vehicle lamp as claimed in claim 11, wherein said second diffusion lens part is formed by subjecting an inner surface of said cover lens to graining treatment and then to frosting treatment.

13. The vehicle lamp as claimed in claim 8, wherein said third diffusion lens part corresponds to a region of said cover lens which locates slightly behind the lowermost end point of said cover lens, said third diffusion lens art has an area which is the sum of the areas of said first and second diffusion lens parts.

14. The vehicle lamp as claimed in claim 13, wherein said third diffusion lens part is formed by subjecting an inner surface of said cover lens to graining and then to frosting treatments.

15. The vehicle lamp as claimed in claim 1, wherein the lamp comprises a single lamp positioning substantially at a middle of an upper peripheral edge of the license plate, said diffusion lens portion which is in the form of steps diffuses vertically the output light of said light source, and a pair of said plain lens portions are formed on both right and left sides of said diffusion lens portion.

16. The vehicle lamp as claimed in claim 1, wherein said diffusion lens portion and said plain portions are bisymmetrical.

17. The vehicle lamp as claimed in claim 1, wherein the lamp comprises a pair of lamps which position near and obliquely backwardly of the middle parts of the right and left edges of the license plate Amendments to the cakns have been fled M folows 1. A vehicle lamp positioning near the periphery of a license plate of a vehicle to illuminate the license plate, the vehicle lamp comprising a light source; and a lens covering the light source, the lens having a first part formed from a diffusion lens portion located near a straight line connecting the light source and a part of the license plate which is closest to the light source, and a second part formed from a plain lens portion located near straight lines connecting the light source and parts of the license plate which are farthest from the light source.

2. A vehicle lamp as claimed in claim 1, wherein the first part of the lens has been subjected to a frosting treatment.

3. A vehicle lamp as claimed in claim 1, wherein the first part of lens has been subjected to a graining treatment.

4. A vehicle lamp as claimed in claim 1, wherein the first part of the lens is formed with lens steps.

5. A vehicle lamp as claimed in claim 1, wherein the first part of the lens has been formed with a combination of at least two of frosting treatment, graining treatment and lens steps.

6. A vehicle lamp as claimed in any one of the preceding claims, wherein the diffusion lens portion is formed on an inner surface of the lens.

7. A vehicle lamp according to any one of claims 1 to 5, wherein the diffusion lens portion is formed on an outer surface of the lens.

8. A vehicle lamp as claimed in claim 1, wherein the diffusion lens portion of the lens comprises first, second and third diffusion lens parts.

9. A vehicle lamp as claimed in claim 8, wherein the first diffusion lens part corresponds to a region of the lens extending from the lowermost end point of the lens near to the front part of the latter.

10. A vehicle lamp as claimed in claim 9, wherein the first diffusion lens part is in the form of more than one step, and is frosted.

11. A vehicle lamp as claimed in any one of claims 8 to 10, wherein the second diffusion lens part corresponds to a region of the lens which is closer to the front part of the letter than the first diffusion lens part.

12. A vehicle lamp as claimed in claim 11, wherein the second diffusion lens part is formed by subjecting an inner surface of the lens to graining treatment and then to frosting treatment.

13. A vehicle lamp as claimed in any one of claims 8 to 12, wherein the third diffusion lens part corresponds to a region of the lens which is located slightly behind the lowermost end point of the lens, the third diffusion lens part having an area which is the sum of the areas of the first and second diffusion lens parts.

14. A vehicle lamp as claimed in claim 13, wherein the third diffusion lens part is formed by subjecting an inner surface of the lens to graining and then to frosting treatments.

15. A vehicle lamp as claimed in claim 1, wherein the lamp comprises a single lamp positioning substantially at a middle of an upper peripheral edge of the license plate, the diffusion lens portion, which is in the form of steps, diffuses vertically the output light of the light source, and a pair of the plain lens portions are formed on right and left sides of the diffusion lens portion.

16. A vehicle lamp as claimed in claim 1, wherein the diffusion lens portion and the plain portions are bisymmetrical.

17. A vehicle lamp as claimed in claim 1, wherein the lamp comprises a pair of lamps which are positioned near and obliquely backwardly of the middle parts of the right and left edges of the license plate.

18. A vehicle lamp, substantially as described with reference to the accompanying drawings.