Illumination device with anti-glare plate

An exemplary illumination device includes a solid-state light source and an anti-glare plate. The solid-state light source is configured for generating light, and the solid-state light source defines a central axis. The anti-glare plate is arranged correspondingly generally adjacent to the solid-state light source. The plate includes an incident surface and an output surface at opposite sides thereof. The output surface has parallel micro-structures each have a length parallel to a first reference axis, and the micro-structures is arranged in two groups at opposite sides of the central axis. The micro-structures are configured for contracting a radiating range of the light entering the plate. Such contraction is along respective opposite directions of a second reference axis, and the second reference axis is substantially perpendicular to the first reference axis.

BACKGROUND

1. Technical Field

The disclosure generally relates to illumination devices, and particularly to an illumination device having an anti-glare plate.

2. Description of Related Art

Nowadays, light emitting diodes (LEDs) are extensively used as light sources due to their high luminous efficiency, low power consumption and long lifespan. Although LEDs can emit bright light to illuminate a dark environment, when bright light from the LEDs directly enters a person's eyes, he/she is liable to experience uncomfortable glare. For example, as shown inFIG. 7, in a typical application of the LEDs10, the LEDs10are arranged on a ceiling to provide overhead lighting. Because the LEDs10emit light radially, a person is liable to directly view light from those LEDs10which are in a range or purview from about 45 degrees to about 85 degrees, as measured from the vertical. The person may thus suffer from glare. Glare can cause eye strain and fatigue, and may lead to headaches and other discomfort.

Therefore, what is needed is an illumination device that overcomes the described limitations.

DETAILED DESCRIPTION

Embodiments of the invention will now be described in detail below, with reference to the drawings.

Referring toFIG. 1, an illumination device100, according to a first embodiment, is shown. The illumination device100has anti-glare function, and includes a solid-state light source11and an anti-glare plate15.

The solid-state light source11may for example be an LED or an LED chip. In this embodiment, the solid-state light source11is an LED11providing a Lambertian light intensity distribution, as illustrated inFIG. 2. The Full Width at Half Maximum (FWHM) of the LED11is in a range from about 0 degrees to about 60 degrees, and also in a range from about 300 degrees to about 360 degrees. That is, the FWHM of the LED is about 120 degrees. The LED11defines a central axis M, which passes through the plate15. The central axis M is parallel to a Z-axis of a defined Cartesian coordinate system, as shown inFIG. 1. The illumination device100may further include a substrate13; thereby, the LED11can be secured on the substrate13. The substrate13may for example be a circuit board.

In the illustrated embodiment, the plate15has a generally cuboid shape. The plate includes an incident surface150and an output surface152at opposite sides thereof. The incident surface150is a planar surface, and the incident surface150and the output surface152are substantially parallel with one another. The incident surface150faces the LED11. The plate15can be made of transparent or light-pervious material, such as glass, resin, silicone, epoxy, polyethylene terephthalate, polymethyl methacrylate or polycarbonate. Alternatively, the plate15can be made of other suitable transparent or light-pervious material.

The plate15defines a plurality of micro-structures155thereon. Each of the micro-structures155extends along a direction parallel to an X-axis of the Cartesian coordinate system. The X-axis is perpendicular to the Z-axis. All the micro-structures155are parallel with one another, and adjoin one another. In the illustrated embodiment, each of the micro-structures155is an elongate protrusion, which extends outwardly from the output surface152of the plate15. In one embodiment, the micro-structures155can be provided by defining a plurality of grooves in the output surface152.

Each of the micro-structures155may have a triangular, trapezoidal, or hemicycle-shaped cross section taken in the YZ-plane. In the illustrated embodiment, the cross section of each micro-structure155is a triangle. A vertex angle θ of the triangle is preferably equal to or larger than 33 degrees. Each micro-structure155includes a first surface155A, and a second surface155B adjoining the first surface155A. The first surface155A is located at a side of the micro-structure155farther away from the central axis M. The second surface155B is located at the other side of the micro-structure155nearer to the central axis M. Preferably, the second surface155B is parallel to the XZ-plane. In the illustrated embodiment, the second surface155B of each micro-structure155adjoins the first surface155A of the neighboring micro-structure155. In alternative embodiments, the second surface155B of each micro-structure155can be adjacent to the first surface155A of the neighboring micro-structure155but not adjoin such first surface155A.

The micro-structures155are arranged in two groups, which are symmetrically opposite to each other across the central axis M. Thereby, two arrays of micro-structures15A,15B are defined at two sides of the central axis M. The micro-structures155of the two arrays of micro-structures15A,15B are symmetrical relative to each other across the central axis M.

In operation, when electric current is applied to the LED11, the LED11emits light L. The light L enters the plate15through the incident surface150. The light L then passes through the plate15to the micro-structures155. The micro-structures155, for example, refract the light L. Thereby, the first and the second surfaces155A,155B provide refracted light L that exits the micro-structures155, with a radiating range of the refracted light L being contracted. In particular, the contraction is in positive and negative Y-axis directions of the Cartesian coordinate system. The Y-axis is perpendicular to the both the X-axis and the Z-axis. Overall, a declination of the light L relative to the central axis M decreases when the light L passes through the micro-structures155. That is, the radiating range of the output light along the Y-axis directions is reduced.FIG. 3shows the light intensity distribution of the LED11after the light L has passed through the plate15. The FWHM along the Y-axis is in a range from about 0 degrees to about 45 degrees, and also in a range from about 315 degrees to about 360 degrees. That is, the FWHM of the LED11after the light L has passed through the plate15is about 90 degrees, which is smaller than the FWHM of the LED11before the light L passes through the plate15(120 degrees). Therefore, the illumination device100has an optimum radiating range suitable for many applications.

In a typical application, the illumination device100is used to provide overhead lighting, as shown inFIG. 4. Most of the light L emitting from the illumination device100is substantially parallel to the central axis M of the LED11, and a viewing direction of a user N may be in a range from about 45 degrees to about 85 degrees, as measured from the vertical. Thus even when the purview of the user N is in the range from about 45 degrees to about 85 degrees, the light L does not directly enter the eyes of the user N, and glare can be avoided.

Referring toFIG. 5, an illumination device200, according to a second embodiment, is shown. The illumination device200includes a solid-state light source21, a substrate23, and an anti-glare plate25. The plate25includes an incident surface250and an output surface252. The illumination device200is similar in principle to the illumination device100of the first embodiment. However, in the illumination device200, a plurality of micro-structures255are formed on the incident surface250, not on the output surface252. In addition, a bonding layer27is provided to interconnect the solid-state light source21and the substrate23with the plate25.

The bonding layer27is made of transparent or light-pervious material, such as resin or silicone. In this embodiment, the solid-state light source21is a light emitting diode chip21. The light-pervious layer27can be used to encapsulate the light emitting diode chip21.

FIG. 6illustrates an illumination device300, according to a third embodiment. The illumination device300is similar to the illumination device100of the first embodiment, and includes a solid-state light source (not labeled), a substrate33, and an anti-glare plate35. The plate35includes an incident surface350and an output surface352at opposite sides thereof. A plurality of elongated first micro-structures355are formed on the output surface352. Each of the first micro-structures355extends parallel to the X-axis. The illumination device300differs from the illumination device100in that the plate35further has a plurality of second micro-structures358formed on the incident surface350. Each of the second micro-structures358extends parallel to a Y-axis. In addition, the solid-state light source (not labeled) includes a plurality of LEDs31, which are arranged on the substrate33in a line parallel to the Y-axis. In the illustrated embodiment, there are three LEDs31.

The shapes and the arrangement of the second micro-structures358formed on the incident surface350are similar to those of the first micro-structures355formed on the output surface352, except that each of the second micro-structures358extends parallel to the Y-axis, whereas each of the first micro-structures355extends parallel to the X-axis. That is, each of the second micro-structures358is arranged perpendicular to each of the first micro-structures355.

The first micro-structures355contract a radiating range of the output light along positive and negative Y-axis directions. The second micro-structures358contract the radiating range of the output light along positive and negative X-axis directions. Thus, glare can be avoided in both X-axis directions and Y-axis directions.

It can be understood that the above-described embodiments are intended to illustrate rather than limit the invention. Variations may be made to the embodiments without departing from the spirit of the invention. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention.