1. Field of the Invention
The present invention relates to a lens module for LED light sources, and more particularly to a lens module capable of shifting illumination areas.
2. Brief Description of the Related Art
Recently, considering the requirements of energy-saving and environmental protection, lighting equipment manufacturers and research units gradually employ light emitting diodes (LED) as light sources in lighting equipment. The LED is a solid semiconductor device that can convert electrical energy directly into light. The LED has advantages such as small volume, short response time, low power consumption, and low contamination.
However, comparing to conventional light sources, LED has a smaller light divergence angle and thus light emitted therefrom is more concentrated, causing brightness differences between the central section and the peripheral section of the illuminated area; that is, the light source may not have uniform illumination. Therefore, many lighting equipment employ secondary optical lenses to alter the optical characteristics of the LED. LEDs of different purposes should be used with different kinds of lenses to achieve different lighting effects.
The LED currently used in road lamp is disposed in an LED lens; this allows light emitted from the LED to be deflected and refracted, to adjust the light projection direction. However, road lamps are generally disposed at road-sides, and since the refracting surface of conventional lens is usually a simple spherical surface or an aspheric structure, the light emitted from the LED therein is concentrated at the area below the road lamp and may not provide uniform illumination on the road. Thus, it results in ineffective street illumination.
Therefore, in order to solve the foregoing problems, Taiwan utility model patent No. M420709 provides a light incident surface (the surface facing the LED) of the lens body; the light incident surface is consisted of three curved surfaces. By the improved lens structure, light emitted from the LED provides uniform illumination on the road, increasing the illumination range, and reduce occurrence of glare.
However, the illumination demands of a road-side and a road are different. The illumination area of a road is larger than that of a road-side, and the illumination uniformity demands of a road is higher than that of a road-side. Accordingly, a light deflection effect is further required to direct the light to the road, thereby increasing the utilization rate of the light source of the road lamp.