introduction
With the rapid development of the world economy, lighting, as an indispensable part of daily life, has become an important energy consumption in countries all over the world. It is well known that LEDs are used instead of incandescent lamps as illumination sources. It is known as another invention of human beings in the field of illumination after Edison invented incandescent lamps. In September 1999, the State Economic and Trade Commission issued 5/China Green Lighting Project 0 Implementation Plan 6, aiming to develop and promote high-efficiency lighting fixtures in China, gradually replacing traditional low-efficiency lighting sources, saving lighting power, and establishing high-quality, efficient and economical comfort. The lighting environment is safe, reliable, environmentally friendly, and improves people's quality of life and improves work efficiency to meet the growing demand for lighting quality and lighting environment in various sectors of the national economy and the people. Of course, to meet the higher requirements for lighting quality and visual environmental conditions, energy reduction cannot be achieved by reducing lighting standards. Instead, it is necessary to improve the lighting engineering design level and methods and improve the efficiency of lighting equipment by fully utilizing modern technology. Conventional incandescent lamps and fluorescent lamps obviously cannot meet the requirements for use, and metal halide lamps and high-pressure sodium lamps with high luminous efficiency are not suitable for general illumination. Light Emitting Diode (LED) is a kind of semiconductor solid-state light-emitting device. It has the unique advantages of long life and low consumption. It plays an environmentally friendly and energy-saving role, making LED light source have a bright future. However, since the brightness of the LED is not required in some cases, how to improve the brightness of the LED illumination is imminent.
1 Scheme to improve the brightness of LED lighting
1. 1 concept of brightness
In order to characterize the optical properties of the illuminating surface in different directions, the concept of brightness is introduced. The light source indicates that the ratio of the intensity dA of a bin at a point in a given direction to the orthographic area of ​​the bin on a plane perpendicular to a given direction is referred to as the brightness of the source in this direction:
1. 2 Improve the brightness by installing a rotating parabolic reflector
1. 2. 1 Optical properties of paraboloids
A rotating parabolic reflector is what we usually call a parabolic reflector, which is a spatial surface obtained by rotating a parabola around its axis of symmetry. Figure 1 shows the parabola obtained by cutting the paraboloid of revolution along the axis of symmetry.
Let the equation of the parabola be
Y2= 2px ( 2)
The main axis is the x-axis, the focal coordinate is F( p2, 0), and a point A on the parabola is set. If the abscissa is x0, the ordinate is y0=2px0, that is, the coordinate of point A is A(x0, 2px0). . Deriving x in the equation gives the tangent slope of the parabola at point A, ie
Let the slope of the reflected light reflected by the paraboloid be k2, and the law of reflection knows that the incident angle is equal, so the nature of the linear equation is
This equation shows that the reflected ray is parallel to the x-axis, which also illustrates the important optical properties of the parabola. After the light emerging from the focus is parabolically reflected, the reflected ray is parallel to the symmetry axis of the paraboloid.
1. 2. 2 LED and parabolic reflector
As mentioned above, when light emerges from the parabolic focus, its reflected light on the paraboloid will be parallel. Since the LED has two lead frames, it is impossible to place the entire LED in the reflector. Therefore, a parabolic surface with holes is used in practice to facilitate the placement of the LEDs, and at the same time, it is advantageous to save materials and reduce costs, as shown in FIG. There is a hole parabolic reflector, the LED part is inserted into the reflector, and the resulting system structure is shown in Figure 2.
The depth at which the LED is inserted into the reflector is an important parameter that relates to the longitudinal length of the entire system and the increase in normal light intensity. The distance between the apex of the LED front end and the incident end of the paraboloid is defined as the insertion depth R. When the vertex of the spherical surface is defined to the left of the incident end, R is positive, and vice versa. By moving the relative position of the reflector to the LED, the intensity and brightness of the light are tested by a test instrument to obtain an optimum insertion depth.
The advantages of this solution: It can effectively improve the brightness of LED lighting fixtures.
Disadvantages: Increased the cost of LED lighting fixtures.