Secondary optical lens of LED street lamp and design method thereof

Abstract

The invention relates to a secondary optical lens of an LED street lamp. The lens is provided with an outer surface, a base face and an inner surface which define an integral structure of the lens together; the outer surface consists of two local ellipsoidal surfaces and a transition surface between the two local ellipsoidal surfaces; the base face is a plane and is crossed with the outer surfaceto form a boundary line of the base face; the inner surface is positioned in the center of the base face and consists of non-hemispherical special curved indents with different curvature radiuses in two directions along a road extending direction and vertical to the road extending direction; the inner surface is symmetrical in front and back, left and right relative to a normal vertical to the base face and passing through the center of the base face; and the outer surface has a symmetric plane passing through an ellipsoidal center connecting line of the two local ellipsoidal surfaces of the outer surface, and an included angle of the symmetric plane and the base face is 60 and 90 degrees.

Description

technical field [0001] The invention relates to the application field of LED lighting, in particular to a secondary optical lens of an LED street lamp and a design method thereof. Background technique [0002] With the development trend of energy saving, emission reduction and green environmental protection, LED (Light Emitting Diodes, Light Emitting Diodes) has been more and more widely used due to its advantages of energy saving and environmental protection, high luminous efficiency, long life, and high color rendering index. A new type of solid light source, which has a tendency to replace traditional street light sources (high-pressure sodium lamps, high-pressure mercury lamps, and metal halide lamps, etc.) in urban road lighting sources. [0003] However, the light emission of LED street lamps is composed of a single LED light source (one-time packaged LED chip). Since the LED light source generally used in street lamps is a Lambertian light source, the luminous directi...

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Problems solved by technology

[0003] However, the light emission of LED street lamps is composed of a single LED light source (one-time packaged LED chip). Since the LED light source generally used in street lamps is a Lambertian light source, the luminous direction is strong. At a certain height from the road and perpendicular to the When the road surface emits light, only a small circular spot can be formed on the road surface, the brightness decreases sharply from the center of the circle to the outside, and the illumination uniformity is low. Therefore, secondary optical design is required to form a relatively rectangular spot on the road surface. Large uniform light spot, because only a rectangular light spot can achieve seamless connection on the road surface, uniformly illuminate the entire road, and achieve the best lighting effect

[0004] Selecting a lens for secondary optical design is the most direct and effective method, but the existing technology often only designs the outer surface of the lens, while ignoring the design of the concave surface (inner surface) in the center of the lens base surface for placing the LED light source

The lens design only for the outer surface limits the improvement of the lens to the direction of light emitted by the LED and the shape of the spot, and cannot well control the distribution of the outgoing light, so that the shape of the spot on the road is not close to the ideal rectangle, and the uniformity bad

[0005] The second shortcoming of the prior art is that it does not take into account that the street lamps are installed on the edge of the road, rather than the center of the road, when the actual road application is not taken into account. The prior art that adopts a symmetrical design just cannot play a role in this occasion, because the prior art The light spots formed on the road surface are symmetrical to the front, rear and left and right of the installation position of the street lamp, and the street lamp is on the edge of the road, so a large part of the light will inevitably shine outside the road surface, resulting in a waste of light energy and reducing the light efficiency.

However, the oblique placement of the street lamp head not only cannot solve this problem perfectly, but also causes the deformation of the road spot shape, changing from a rectangle to a trapezoid, which reduces the uniformity of illumination.

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