Beam Shaping Freeform Lens Design With Modified Optical Flux Partition

A freeform lens design strategy that performs directivity transformation is proposed. In principle, arbitrary beam pattern can be achieved with this method, which uses a modified flux partition method. Taking a Lambertian light source as the example, this method successfully give different required intensity distributions, such as the isotropic and exponential ones. Also, the isotropic directivity lens is fabricated and the beam pattern is measured to verify the effectiveness. With a real Lambertian top emitting white light LED as the source, the experimental results agree well with the simulation ones, which provides high directivity isotropy (more than 80%). This scheme takes Fresnel loss of the lens into consideration and can also predict the efficiency of the lens; it may find applications in lighting or illumination engineering where directivity transformation are required.