Design of LED light therapy device based on free-form lens

The angle between the LED light therapy instrument and the skin will have an impact on the light penetration effect, which interferes with the development of the light treatment dose, resulting in the final light treatment effect does not achieve the desired goal. To address this problem, this paper proposes a new design scheme using a COB packaged LED light source with a 10mm diameter light emitting surface, using a free-form lens with a Fresnel lens for light leveling and collimation. The initial design of the free-form lens is based on the edge light theory, Snell's law and energy mapping method. The distance between the light source and the target surface is set to 200 mm, the diameter of the target surface is 400 mm, and finally the Fresnel lens is chosen to collimate the treatment light emitted from the LED light source. Simulation results show that a treatment spot with a diameter of 220 mm and a uniformity of more than 85% can be produced within the range of 50 to 150 mm after this optical path system, and the divergence angle of the spot is controlled within 10°. This design is able to produce a large size therapeutic spot in the near field with both uniformity and collimation, which makes up for the shortcomings of the traditional LED phototherapy instrument design and provides an important reference for the design of LED phototherapy instruments.