LIGHTING ASSEMBLY

Abstract

A lighting assembly includes a light source, a light guiding plate and a reflecting member. The light guiding plate has a light input surface, a light output surface extending from the light input surface, a connecting surface and a reflecting surface. The connecting surface has an inclined segment. Extensions of the inclined segment and the light output surface cooperatively define a first included angle. The reflecting surface interconnects the connecting surface and the light output surface, cooperates with the light output surface to define a second included angle, and mounted with the reflecting member. A thickness of the light guiding plate at the reflecting surface is greater than that at the light input surface.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an optical device, more particularly to a light guiding assembly incorporating a light guiding device and a light source.

2. Description of the Related Art

A long fluorescent lamp or multiple round light bulbs are often used in exhibition venues where sufficient lighting for a long or large display area is required. However, the light emitted by a single fluorescent lamp tends to be scattered and inefficient, and the light from multiple round light bulbs tends to overlap and is thus uneven. In addition, increasing the number of lamps also increases the costs of lighting.

A light guiding device is often used to regulate light emitted from a light source for a more even lighting effect. U.S. Pat. No. 6,328,453 and U.S. Pat. No. 6,752,507 disclose light guiding plates with micro structures formed thereon for controlling directions of light outputted from the light guiding plates to result in a relatively even lighting effect. However, designing and processing the micro structures on the light guiding plates increases the manufacturing complexity and costs.

SUMMARY OF THE INVENTION

Therefore, the object of the present invention is to provide a lighting assembly including a light guiding device that is able to manipulate an illuminating region without micro structures to alleviate the aforesaid drawbacks of the prior art.

According to the present invention, a lighting assembly includes a light source capable of emitting light, a light guiding plate and a reflecting member. The light guiding plate has a light input surface, a light output surface, a connecting surface and a reflecting surface. The light output surface extends from the light input surface. The connecting surface is opposite to the light output surface and has an inclined segment inclining away from the light output surface. Extensions of the inclined segment and the light output surface cooperatively define a first included angle therebetween. The reflecting surface interconnects the connecting surface and the light output surface, and cooperates with the light output surface to define a second included angle therebetween. A thickness of the light guiding plate at the reflecting surface is greater than that at the light input surface. The reflecting member is mounted to the reflecting surface of the light guiding plate.

The lighting assembly according to the present invention is able to regulate scattered light emitted from the light source into an even light projection that is suitable for illuminating a large area. The parameters of the light guiding plate can be changed during the manufacturing process to control the luminous flux of the light exiting the light guiding plate.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the present disclosure will become apparent in the following detailed description of the preferred embodiment with reference to the accompanying drawings, of which:

FIG. 1 is an exploded perspective view of a preferred embodiment of a lighting assembly according to the present invention;

FIG. 2 is a side view of a light guiding device of the preferred embodiment; and

FIG. 3 is a side view of a variation of the light guiding device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference to FIG. 1, the preferred embodiment of a lighting assembly 2 according to the present invention includes a light guiding device 20 and a light source 21. The light guiding device 20 includes a light guiding plate 22 for receiving light emitted from the light source 21, and a reflecting member 23 mounted to the light guiding plate 22. In this embodiment, the light source 21 includes a plurality of light emitting diodes (LEDs) 211, but it is not limited thereto.

With further reference to FIG. 2, the light guiding plate 22 has a light input surface 221, a light output surface 222, a connecting surface 223 and a reflecting surface 224. The light input surface 221 has a first edge 225 and a second edge 226 opposite to each other in a first direction (D1). The light output surface 222 extends from the first edge 225 of the light input surface 221 in a second direction (D2) transverse to the first direction (D1), and has a distal edge 230 opposite to the first edge 225 of the light input surface 221. The connecting surface 223 is opposite to the light output surface 222 in the first direction (D1), and has a straight segment 229 extending from the second edge 226 of the light input surface 221 and an inclined segment 220 extending from the straight segment 229, inclining away from the light output surface 222 and terminating at an end edge 227. In this embodiment, the straight segment 229 of the connecting surface 223 is parallel to the light output surface 222. The reflecting surface 224 interconnects the end edge 227 of the connecting surface 223 and the distal edge 230 of the light output surface 222. Extensions of the inclined segment 220 of the connecting surface 223 and the light output surface 222 cooperatively define a first included angle θ therebetween. The reflecting surface 224 and the light output surface 222 cooperatively define a second included angle φ therebetween. A distance between the second edge 226 of the light input surface 221 and the end edge 227 of the connecting surface 223 in the second direction (D2) is shorter than that between the first edge 225 of the light input surface 221 and the distal edge 230 of the light output surface 222.

With the above mentioned configuration, relationships of θ<φ, θ<θ_T and L≧(AD)/tan θ are satisfied, where θ_T is a critical angle for total internal reflection associated with the light guiding plate 22, (AD) is a distance between a location of incidence of a light beam on the light input surface 221 and one of the first edge 225 and the second edge 226 of the light input surface 221, and (L) is the distance between the second edge 226 of the light input surface 221 and the end edge 227 of the connecting surface 223 in the second direction (D2). The second included angle φ is a parameter for controlling an angle of beam exiting the light guiding plate 22, and the distance (L) and the first included angle θ are parameters for controlling a width of beam exiting the light guiding plate 22. These three parameters cooperatively control the luminous flux of the light exiting the light guiding plate 22.

The reflecting member 23 is mounted to the reflecting surface 224 of the light guiding plate 22. The light emitted by the light source 21 enters the light guiding plate 22 via the light input surface 221, and part of the light is reflected by the reflecting member 23 to exit the light guiding plate 22 through the light output surface 222.

Light guiding plates 22 of two different materials, Polycarbonate (PC) and Polymethylmethacrylate (PMMA), and with different dimensions are made for testing purposes. In the tests, the light measured at the light input surface 221 is 90.67 lm, and the LEDs 211 of the light source 21 were linearly arranged and correspond in position to the central axis of the light input surface 221 (see FIG. 1), such that AD=(d/2) where (d) is the distance between the first edge 225 and the second edge 226 of the light input surface 221. The light output of each test group is measured in lm and percentages of the light output with respect to the light input are computed, and the test results are shown in Tables 1 and 2.

It is noted herein that AD may vary depending on the position and orientation of the LEDs 211 that affect the angle and position of incidence of the light beam on the light input surface 221. A condensed lighting effect may still be achieved if AD is varied such as when AD is 0.3 d or 0.7 d.

Referring to Table 1, test group (1) satisfies all the above mentioned three relationships where θ<φ (11°<30°), θ<θ_T (11°<42.16°) and L≧(d/2)/tan θ (79 mm>2.2 mm). Therefore, 90% efficiency is achieved. Test group (2) has a similar result to group (1).

Test groups (3) to (6) show that the efficiency is reduced proximately to 50% or less if any of the three relationships is not satisfied.

TABLE 1
Material	PMMA
Index of	1.49
Reflection
(n)
Critical	42.16°
Angle
(θ T)
d (mm)	4
(d/2)/(tanθT) (mm)	2.2
Flux of	90.67
light at
the light
input surface
(lm)
L (mm)	79	79	79	79	2	79
φ	30	44	44	44	44	44
θ (°)	11	11	42.16	44	11	50
Flux of	81.8	86.5	47.4	48.1	42.2	48.8
light at the
light output
surface (lm)
Ratio of	90.2	95.4	52.3	53	46.5	53.8
Light
Output to
Light Input
(%)
Test Group Number	(1)	(2)	(3)	(4)	(5)	(6)

Table 2 indicates similar results from experiments carried out with the light guiding devices 20 whose light guiding plates 22 are made of PC.

TABLE 2
Material	PC
Index of	1.59
Reflection
(n)
Critical	38.97°
Angle
(θ T)
d (mm)	4
(d/2)/(tanθT) (mm)	2.5
L (mm)	79	79	79	79	2	79
φ	30	44	44	44	44	44
θ (°)	11	11	42.16	44	11	50
Flux of	81.8	84.1	46.2	46.7	41.7	47.5
Light Input
from the
Light Guiding
Plate
(lm)
Ratio of	90.2	95.4	50.9	51.5	46	52.4
Light
Output to
Light Input
(%)
Test Group Number	(1)	(2)	(3)	(4)	(5)	(6)

With reference to FIG. 3, an alternative design of the connecting surface 223 without any segment parallel to the light output surface 222 will obtain similar test results to those shown in Tables 1 and 2.

To conclude, the lighting assembly 2 according to the present invention is able to regulate scattered light emitted from the light source 21 into an even light projection that is suitable for illuminating a large area. The parameters of the light guiding plate 22 can be changed during the manufacturing process to control the luminous flux of the light exiting the light guiding plate 22.

While the present invention has been described in connection with what is considered the most practical and preferred embodiment, it is understood that this invention is not limited to the disclosed embodiment but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.

Claims

1. A lighting assembly comprising: a light source capable of emitting light;a light guiding plate having a light input surface,a light output surface that extends from said light input surface,a connecting surface that is opposite to said light output surface, and that has an inclined segment inclining away from said light output surface, extensions of said inclined segment and said light output surface cooperatively defining a first included angle therebetween, anda reflecting surface that interconnects said connecting surface and said light output surface, and that cooperates with said light output surface to define a second included angle therebetween, a thickness of said light guiding plate at said reflecting surface being greater than that at said light input surface; anda reflecting member for reflecting light emitted from said light guiding plate back into said light guiding plate.

2. The lighting assembly of claim 1, wherein said connecting surface further has a straight segment that is connected between said inclined segment and said second edge of said light input surface, and that is parallel to said light output surface.

3. The lighting assembly of claim 1, wherein said light source includes a plurality of light emitting diodes (LEDs) disposed linearly along an axis.

4. The lighting assembly of claim 3, wherein the length of said light input surface is extended along said axis.

5. The lighting assembly of claim 1, wherein said light input surface is a flat surface without serration.

6. The lighting assembly of claim 1, wherein the length a projection of said light output surface on said connecting surface is greater than the length of said connecting surface.

7. The lighting assembly of claim 1, wherein said reflecting surface of said light guide plate is covered by said reflecting member, and no surface of said light guiding plate other than said reflecting surface is covered.

8. The lighting assembly of claim 1, wherein said reflecting surface is slanted with a constant slope rate.

9. The lighting assembly of claim 1, wherein said light output surface is directly exposed to surroundings without being covered.

10. The lighting assembly of claim 1, wherein said light connecting surface is mirror surface without sandblasting.