Lighting device

A lighting device includes a housing, a plurality of LEDs arranged on a base of the housing, and a first optical plate positioned above the LEDs. The first optical plate includes a light input surface, a light output surface opposite to the light input surface, and a plurality of elongated arcuate protrusions formed on the light output surface. The elongated arcuate protrusions are substantially parallel to one another. The lighting device may be used as a backlight module.

CROSS REFERENCE STATEMENT

This application is related to co-pending U.S. patent applications, which are Ser. Nos. 12/317,396, 12/319,010, 12/318,043, 12/319,009, and all entitled “OPTICAL PLATE AND BACKLIGHT MODULE USING THE SAME,” and application Ser. No. 12/319,040, entitled “LIGHTING DEVICE”. In the co-pending applications, the inventor is Shao-Han Chang. The co-pending applications have the same assignee as the present application.

BACKGROUND

1. Technical Field

The present invention generally relates to lighting devices and, more particularly, to a lighting device using light emitting diodes.

2. Discussion of the Related Art

Light emitting diodes (LEDs) are preferred over other types of light sources because LEDs exhibit low energy consumption, long service life, and other advantages. Therefore, LEDs are widely used as light sources.

Typically, a lighting device using LEDs includes a housing and a plurality of LEDs arranged on a base of the housing. In use, light rays emitted from different LEDs of the lighting device illuminate an object, thereby creating a lot of shadows of the object. Thus, a lighting quality is reduced.

Therefore, a new lighting device is desired to overcome the above-described shortcomings.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Referring toFIG. 1, one embodiment of a lighting device200includes a housing22, a plurality of LEDs24arranged on a base of the housing22, a first optical plate26, and a second optical plate28. The first optical plate26is positioned above the LEDs24and the second optical plate28is positioned above the first optical plate26. The first optical plate26is spaced from the base of the housing22at a predetermined distance. The first optical plate26and the housing22cooperatively define a first light-mixing space31. The second optical plate28is spaced from the base of the first optical plate26at a predetermined distance, so that a second light-mixing space32is defined between the first optical plate26and the second optical plate28.

In one embodiment, the housing22is made of metal or plastic materials with high reflectivity. In another embodiment, an interior surface of the housing22may be coated with a high reflectivity coating for improving light reflectivity rate.

Referring toFIG. 2andFIG. 3, the first optical plate26has a light input surface260and an opposite light output surface262. The light input surface260may be a flat surface adjacent to the LEDs24. The light input surface260of the first optical plate26faces the LEDs24and the light output surface262of the first optical plate26faces away from the LEDs24. Light enters the first optical plate26via the light input surface260.

The light output surface262of the first optical plate26forms a plurality of elongated U-shaped protrusions264substantially parallel to one another. In one embodiment, a cross-section of the elongated arcuate protrusions264may be substantially semi-circular.

A pitch P1between adjacent elongated arcuate protrusions264is about 0.025 millimeters (mm) to about 1.5 mm. A radius R1of the elongated arcuate protrusions264is about P1/4 to about 2P1. A maximum height H1of the elongated arcuate protrusions264is about 0.01 mm to about R1. For example, if the pitch P1is 0.275 mm, the radius R1may be about 0.1375 mm, and maximum height H1may be about 0.11 mm.

In another embodiment, a cross-section of the elongated arcuate protrusions264may be a substantially semi-elliptical curve.

A thickness of the first optical plate26may be about 0.4 mm to about 4 mm. The first optical plate26may be made of a material such as polycarbonate, polymethyl methacrylate, polystyrene, copolymer of methyl methacrylate and styrene, and any suitable combination of those.

The first optical plate26may be integrally formed by injection molding technology, so that the first optical plate26has a stronger rigidity and mechanical strength. Thus, the first optical plate26has a relatively high reliability.

The structure and material of the second optical plate28may be the same as that of the first optical plate26. When the first optical plate26and the second optical plate28are employed in the lighting device200, an extending direction of the elongated arcuate protrusions264of the first optical plate26may be substantially perpendicular to an extending direction of a plurality of elongated arcuate protrusions of the second optical plate28. A protecting plate to protect the second optical plate28is unnecessary because of the strong rigidity and mechanical strength of the elongated arcuate protrusions on the second optical plate28.

In the illustrated embodiment, the first optical plate26and the second optical plate28are received in the housing22. The first optical plate26and the second optical plate28may adhere to a sidewall of the housing22, or be supported by a bracket.

The predetermined distance between the first optical plate26and the base of the housing22, and the predetermined distance between the second optical plate28and the first optical plate26may be varied. In one embodiment, a depth of the housing22is inversely proportional to the number of the LEDs24. For example, if the number of the LEDs24is large, the depth of the housing22is small, and the predetermined distance between the first optical plate26and the base of the housing22, and the predetermined distance between the second optical plate28and the first optical plate26are short. If the number of the LEDs24is small, the depth of the housing22is large, and the predetermined distance between the first optical plate26and the base of the housing22, and the predetermined distance between the second optical plate28and the first optical plate26are long.

Referring toFIG. 1again, in use, light from the LEDs24diffuses in the first light-mixing space31. When the light travels through the first optical plate26, the light is refracted, reflected, and diffracted due to the plurality of elongated arcuate protrusions264on the light output surface262of the first optical plate26. Thus, a relatively uniform surface light source is achieved.

After light travels through the first optical plate26, light is diffused in the second light-mixing space32. The light is refracted, reflected, and diffracted via the second optical plate28. Therefore, in the lighting device200, strong light spots of the light sources seldom occurs, and more uniform light is obtained.

In use, light emitted from the lighting device200is uniform to create a virtually single light source. When the lighting device200is used to illuminate an object, a single shadow of the object is formed. The first optical plate26and the second optical plate28may enhance the efficiency of light utilization and increase the brightness of the outputted light. The brightness of the lighting device200may increase by as much as 22 percent by using the first optical plate26and the second optical plate28.

In an alternative embodiment, the lighting device200may further include at least one optical sheet positioned on the second optical plate28. In such cases, the lighting device200may be used as a backlight module applied in a liquid crystal display. The optical sheet may be a diffusion sheet, a prism sheet, or a reflective polarizing sheet. The optical sheet may collimate an emitted light, thereby improving the brightness of light illumination and outputted light of the backlight module is uniform. The backlight module may also have a thin thickness.

Referring toFIG. 4, a second embodiment of a first optical plate36includes a light input surface360and an opposite light output surface362. The first optical plate36is similar to the first optical plate26, except that the light input surface360defines a plurality of elongated arcuate troughs363substantially parallel to one another. An extending direction of the elongated arcuate troughs363is substantially parallel to an extending direction of a plurality of elongated arcuate protrusions364formed on the light output surface362.

A cross-section of the elongated arcuate troughs363is substantially semi-circular. A pitch P2between adjacent elongated arcuate troughs363is about 0.025 mm to about 1 mm. A radius R2of the elongated arcuate troughs363is about 0.006 mm to about 2 mm. A maximum depth H2of the elongated arcuate troughs363is about 0.01 mm to about 2 mm. In an embodiment, a cross-section of the elongated arcuate troughs363may be a substantially semi-elliptical curve.

Referring toFIGS. 5 and 6, a third embodiment of first optical plate46includes a light input surface460and an opposite light output surface462. The first optical plate46is similar to the first optical plate26, except that a plurality of elongated arcuate protrusions464and a plurality of V-shaped ridges466are alternately formed on the light output surface462. The elongated arcuate protrusions464and the V-shaped ridges466are substantially parallel to one another.

A cross-section of the elongated arcuate protrusions464may be semi-circular. A maximum width D1of the V-shaped ridges466is about 0.025 mm to about 1 mm. A vertex angle θ of the V-shaped ridges466is about 80 degrees to about 100 degrees. A maximum height H3of the V-shaped ridges466is about 0.01 mm to about 3 mm.

A width L1of the elongated arcuate protrusions464is about 0.025 mm to about 1.5 mm. A radius R3of the elongated arcuate protrusions464is about L1/4 to about L1. A maximum height H4of the elongated arcuate protrusions464is about 0.01 mm to about R3. The maximum width D1, the vertex angle θ, the maximum height H3, the width L1, the radius R3, and the maximum height H4, thereby adjusting the brightness of outputted light travelling through the first optical plate46.

Referring toFIG. 7, a fourth embodiment of a first optical plate56includes a light input surface560and an opposite light output surface562. The first optical plate56is similar to the first optical plate46, except that the light input surface560defines a plurality of elongated arcuate troughs563. An extending direction of the elongated arcuate troughs563is substantially parallel to an extending direction of a plurality of elongated arcuate protrusions564and a plurality of V-shaped ridges566of the light output surface562.

Referring toFIG. 8, a fifth embodiment of a first optical plate66includes a light input surface660and an opposite light output surface662. The first optical plate66is similar to the first optical plate56, except that an extending direction of a plurality of elongated arcuate troughs663in the light input surface660is substantially perpendicular to an extending direction of a plurality of elongated arcuate protrusions664and a plurality of V-shaped ridges666of the light output surface662.

Referring toFIG. 9, a sixth embodiment of a first optical plate76is similar to the first optical plate26, except that a light input surface760of the first optical plate76defines a plurality of elongated arcuate troughs763. An extending direction of the elongated arcuate troughs763is substantially perpendicular to an extending direction of a plurality of elongated arcuate protrusions764of a light output surface762.

Referring toFIG. 10, a seventh embodiment of a first optical plate86is similar to the first optical plate76, except that a light output surface862further forms a plurality of V-shaped ridges866. The V-shaped ridges866substantially perpendicularly intersect with a plurality of elongated arcuate protrusions864of the light output surface862.

The structure of the second optical plate28of the lighting device200may be the same as that of the first optical plates26,36,46,56,66,76,86.

It may be appreciated that in the lighting device, the structure of the first optical plate may be different from that of the second optical plate. For example, when the first embodiment of the first optical plate26is used in the lighting device200, the structure of the second optical plate28may be the same as that of the second embodiment of the first optical plate36. Alternatively, the second optical plate28may be omitted.