Optical element and backlight module having the same

#The present invention relates to an optical element, and more particularly to an optical element applicable to a light-emitting component and a backlight module.

#A backlight module is a basic component of an LCD. Currently used backlight modules may be substantially classified into side-lit backlight modules and direct-lit backlight modules.

#The conventional side-lit backlight module has light-emitting diodes arranged in rows at two sides thereof, and a light guide is provided in a visible range of a display, so that light beams produced by the light-emitting diodes are uniformly radiated out of the backlight module through the light guide. U.S. Pat. No. 6,679,621 and US Patent Publication No. 20060076568 both provide an optical element which covers the light-emitting diodes and is embedded into the two sides of the light guide. The optical element is equivalent to a lens in function, and is mainly used to divert the light beams emitted from the light-emitting diodes to make the lights come out in parallel from the two sides of the optical element. Furthermore, a reflective paint is coated on an upper surface of the optical element, so that no light beams will come out from the top of the optical element. Such a design may reduce the thickness of the side-lit backlight module and ensure that all light beams emitted from the light-emitting diodes enter the light guides.

#FIG. 1 is a plan view of an optical element according to the first embodiment of the present invention;

#FIG. 2 is a cross-sectional view of the optical element in FIG. 1;

#FIGS. 3A and 3B are schematic views showing a light beam passing through the optical element of the present invention;

#Referring to FIGS. 1 and 2, a plan view and a cross-sectional view of the optical element 100 (for example, a lens) in the first embodiment of the present invention are shown. As shown in FIG. 2, the optical element 100 includes a bottom surface 120, at least one side refractive surface having a smooth aspherical surface with downward notches (in this embodiment, there are four side refractive surfaces 142, 144, 146, and 148), an upper refractive surface 160, and junction surfaces 152, 154, 156, and 158 connecting the side refractive surface 142 and the upper refractive surface 160 or two adjacent side refractive surfaces. A dashed line 170 is a central axis of the optical element 100 and is perpendicular to the bottom surface 120. Furthermore, an extension plane of any junction surface passes through the bottom surface. The extension plane of any junction surface passes preferably through the center of the bottom surface. It should be noted that although the optical element 100 in FIG. 2 has four side refractive surfaces at the left and right sides, respectively, the number of the side refractive surfaces of the optical element 100 of the present invention is an integer greater than or equal to 1. In this embodiment, the side refractive surface at the left and right sides actually is an annular refractive surface symmetrical about the central axis. Furthermore, in this embodiment, the upper refractive surface 160 is a smooth aspherical surface having an upward notch, or a curved surface of another style, and the section thereof consists of a curve with an upward notch and left and right curves with downward notches. However, according to the other embodiment of the present invention, the section of the upper refractive surface may also be a curve having at least three critical points in which the middle critical point is the lowest point of the curve.

#FIG. 3A is a schematic view showing the light beam passing through the optical element 100. In one embodiment of the present invention, the optical element 100 and a light-emitting diode are assembled into a light-emitting component. However, according to other embodiments of the present invention, other types of light sources instead of the light-emitting diode may also be used to be assembled into a light-emitting component. For example, other light sources may be an incandescent lamp, a phosphor light-emitting device, or another light source. The light-emitting diode may be one or more white light chips, RGB single chips, or RGB chip assembly.

#In this embodiment, the extension plane of the junction surface 152 between the upper refractive surface 160 and the side refractive surface 142 is just connected to an intersection point of the central axis and the bottom surface. If the light source is a perfect point light source or a point light source O with a small light-emitting area, and the first angle α is just an included angle formed between the junction surface 152 and the bottom surface 120, it may be assumed that in the light beam incident into the optical element 100 through the bottom surface, if a part of the light beam having the included angle from the bottom surface is greater than α, this part of the light beam will be refracted by the upper refractive surface and come out, and if a part of the light beam having the included angle from the bottom surface is smaller or equal to α, this part of the light beam will be refracted by the side refractive surface and come out. In this embodiment, a maximum angle formed between the light beam coming out from the side refractive surface and the bottom surface is γ, where γ is smaller than or equal to α. Furthermore, the included angle formed between the light beam to be incident on the upper refractive surface and the central axis of the optical element 100 is β, and a maximum included angle formed between the light beam coming out from the upper refractive surface and the central axis of the optical element 100 is θ, i.e., θ is between the light beam coming out from the edge of the upper refractive surface 160 and the central axis, and is greater than or equal to the included angle β.