Design Of Free-form Surface With Wavefront Reconstruction

Light-emitting diode(LED) is a new kind of light source, with environmental protection, energy saving, high luminous efficiency, long life and other characteristics, so it’s widely used in the lighting industry. However, its outgoing irradiance distribution curve is similar to the lambert light source. Without the secondary optical design, the ideal irradiance effect will not be achieved. Therefore, the secondary optical design is currently a hot topic in illumination. The main secondary optical design methods include CPC, SMS, tailored method, differential equations, etc. However, there are some shortcomings in these methods, such as calculation difficulty, low light efficiency and processing difficulty. To overcome these disadvantages, a new design method with wavefront reconstruction is proposed in the present thesis.The main work and achievements are listed as following:1. The existing design methods, such as tailored method and SMS method, are investigated for proposing our innovative design method.2. Combining equal optical path conditions and Snell’s law, a free-form surface design method with the wavefront reconstruction is presented. A virtual light source, corresponding to an emergent wavefront, is introduced for the lens design. The emergent lights are projected onto the target surface in the form of wavefront. It makes the distribution of the emergent light doesn’t change with the target surface distance, which is more suitable for lighting design. Firstly, for a point light source, a rotational model is constructed by this method.3. For a 5050 LED source, a negative feedback optimization method is proposed. Firstly, the original lens model is used to obtain the irradiance distribution on target plane, which is compared to the desired value. The displacement of discrete points are determined by the feedback function, which is decided by the difference of simulation value and desired value. Using the optimization method, the uniformity increases from 0.8 to over 0.9, and the number of iterations is six.4. In order to verify the third step, the lens model was manufactured and assembled as a simple experimental apparatus. Professional SLR camera was used to record the irradiance distribution on the target surface. The result shows that the experimental data are identical to the simulation result.5. For the arbitrary axisymmetric and rectangular distribution, further design algorithms are proposed. So the design method is of more general and practical usage, and the optical simulations are carried out.