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The higher flexibility of freeforms has opened the possibility to find better solutions than classical surfaces many optical problems, especially those whose specifications (either optical or geometrical) are far from rotational symmetry. For instance, short through distance multimedia projectors cannot be placed in front of the center of the projected image without blocking the spectators’ view, and this requires the projection to be done from one side. Offset rotational symmetric solutions are suboptimal, and a freeform projector can improve the image quality on the target area with the same number of surfaces or can match the quality with fewer optical surfaces 1. Similarly, many head-worn displays are located close to the eyes of the user to make the headset sleeker. In this case, some parts of the physical display are used at very high emitting angles and rotational symmetric cannot provide optimal solutions for this configuration. In nonimaging applications, low-beam headlamps of cars also need to produce an asymmetric pattern on the road to avoid blinding the incoming drivers. Freeforms permit to solve this design problem efficiently, and match aesthetic constraints. The continuous progress in the technology to produce and test freeforms, as occurred in the past with rotational aspherics, is pushing optical designers to consider more and more the use of freeforms in their designs. However, the also higher complexity of these surfaces introduces multiple challenges in their design since traditional design methods have been focused in rotational optics. These challenges go from finding the best mathematical description of the optical surfaces to the design algorithms themselves. We’ll review the main design techniques proposed to design freeforms and illustrating its use in specific examples for several applications.
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