Lens and LED module using the same

An LED module includes a printed circuit board, an LED mounted on the printed circuit board, and a lens fixed on the printed circuit board and covering the LED for refracting light emitted by the LED. The lens has a concaved inner face for incidence of the light and an opposite convex outer face for the light refracting out thereof. The inner face is aspherical. The outer face is spherical. The inner and outer faces are centrosymmetrical relative to axes, respectively, which are coincident with each other. A curvature of the inner face is gradually reduced from a center to an edge thereof.

BACKGROUND

1. Technical Field

The present disclosure relates generally to an LED module, and more particularly to an LED module for lighting and a lens applied in the LED module.

2. Description of Related Art

LED lamp, a solid-state lighting, utilizes LEDs as a source of illumination, providing advantages such as resistance to shock and nearly limitless lifetime under specific conditions. Thus, LED lamps present a cost-effective yet high quality replacement for incandescent and fluorescent lamps.

Known implementations of LED modules in an LED lamp employ lenses for focusing white light generated by the LEDs. Due to a forming mechanism of white light generated by the LEDs, the light pattern provided by the light is prone to be yellow or shining at edges, which is not suitable for illumination.

What is need therefore is a lens and an LED module using the lens which can overcome the above limitations.

DETAILED DESCRIPTION

FIG. 3illustrates, in cross section, an LED module in accordance with an embodiment of the present disclosure. The LED module comprises a printed circuit board10, an LED20mounted on the printed circuit board10and a lens30covering the LED20. Perspective views of the lens30from different aspects are shown inFIGS. 1 and 2. In detail, the LED20is mounted on a substrate201which is electrically connected to the printed circuit board10. A semicircular encapsulant202is secured to the substrate201and covers the LED20. The encapsulant202functions as a primary optical lens and a protector for the LED20. The encapsulant202is made of transparent silicone. The lens30functions as a secondary optical lens for the LED20.

The substrate201can be fixed onto the printed circuit board10by soldering or other means. The number of the LED20can be changed corresponding to a desired lighting intensity. The LED20has a light axis I.

The lens30is integrally made of a transparent material with good optical performance, such as PMMA (polymethyl methacrylate) or PC (polycarbonate). The lens30comprises a base31and a light refracting portion33protruding upwardly from the base31. The base31is substantially disk shaped. A recess310is defined in a middle of a bottom of the base31. A substantially rectangular fixing ear312extends from each lateral side of the base31. Bottoms of the fixing ears312and the base31are fixed onto the printed circuit board10. The fixing ears312cause the lens30to have a large connecting area with the printed circuit board10, thereby making the lens30be more securely connected to the printed circuit board10. Additionally, the fixing ears312function as a member facilitating positioning of the securement of the lens30to the printed circuit board10. A fixing groove314is defined in a bottom of the fixing ear312for receiving glue or the like therein, which is used for adhering the lens30to the printed circuit board10.

The light refracting portion33protrudes upwardly from a middle top of the base31. The light refracting portion33has a concaved inner face303at a bottom thereof and an opposite convex outer face307. The concaved inner face303is exposed to the recess310of the base31. A concaved bottom surrounded by the inner face303of the refracting portion33communicates with the recess310to cooperatively define a receiving room320receiving the LED20therein. The inner face303is provided for an incidence of light generated by the LED20, and the outer face307is provided for refracting the light. The inner face303is concaved to be aspherical and is centrosymmetrical relative to an axis II. The outer face307is convex to be spherical and is centrosymmetrical relative to another axis III which is coincident with the axis II. The axes II, III are also coincident with the light axis I of the LED20when the lens30covers the LED20. Different parts of the inner face303have different curvatures. A curvature of a top end304of the inner face303at a center thereof is larger than that of a bottom end305of the inner face303at an edge thereof, and the curvature of the inner face303reduces gradually from the top end304(i.e., the center) to the bottom end305(i.e., the edge) thereof. In this embodiment, the curvature of the outer face307is 0.215 mm−1. The curvature of the top end304(i.e., the center) of the inner face303is 0.26 mm−1, and the curvature of the bottom end305(i.e., the edge) of the inner face303is 0.15 mm−1.

FIG. 4shows a curve of the light intensity vs. angle for the LED module in accordance with the present disclosure. After the light is refracted by the lens30to leave the outer face307, most of the light, specifically, 95% of the light is located within 30 degrees off the axis I; namely, an illumination angle of the LED module is about 60 degrees. When the light off the axis I is more than about 20 degrees, the light intensity decreases sharply. The curvatures of the inner and outer faces303,307can be altered in different embodiments to focus the light at different ranges such as 30 degrees or 45 degrees.

By a computer analysis, the light pattern formed by the LED module of present disclosure has a uniformly illumination. Compared with the conventional LED module, the light pattern of the present disclosure has no yellow or shining edge, which is more comfortable for users when the LED module is used for illumination application.

Understandably, according to actual requirement, a number of the LED modules can be mounted on the printed circuit board10. The LED modules can be arranged in a matrix or circle or other shape.