What is free surface?

A freeform surface is a surface that does not have a simple mathematical formula or a regular geometric shape, such as a sphere or a cylinder. Instead, it can be described as a complex curvature that is irregular and asymmetric, characterized by mathematical expressions that are relatively intricate and lack rotational symmetry.

What is the principle of free surface?

The principle of free surfaces is to use high-order mathematical equations to design highly complex non-regular surface shapes, thus achieving higher degrees of freedom and better optical performance in optical systems. Compared with traditional spherical or non-spherical shapes, free surfaces offer higher design freedom and more flexible structural forms, enabling more precise and flexible optical control. Therefore, free surfaces are widely used in optical design for designing high-performance non-spherical lenses, non-spherical mirrors, and other optical elements. However, due to the complexity of the design and manufacturing processes of free surfaces, advanced computer-aided design and manufacturing techniques are required to achieve them.

The Application and Advantages of Free Surfaces in Augmented Reality (AR)

Free surfaces have the following advantages over traditional spherical or non-spherical shapes in optical design:

1. Higher design freedom: The shape of free surfaces can be expressed using more complex higher-order mathematical forms, allowing for greater design freedom. This means that more complex and flexible optical control can be achieved to meet different optical design requirements.
2. More flexible structural forms: The structural form of free surfaces can be more flexible, unrestricted by traditional spherical or non-spherical shapes. This can help design more compact, lightweight, and efficient optical systems.
3. Better optical performance: The shape of free surfaces can better control the propagation of light, leading to improved optical performance, such as smaller aberrations and larger field of view. This can improve resolution, clarity, color reproduction, and other metrics of optical systems.
4. Wider range of applications: Free surfaces can be applied to different optical components, such as lenses, reflectors, and diffractive optical elements. This can meet the needs of different application fields, such as photography, laser processing, medical imaging, automotive lighting, etc.

In augmented reality (AR) glasses, free surface solutions can help solve problems such as small field of view, weak immersion, large volume and weight, and poor imaging quality, thus improving the performance and user experience of AR glasses.

Traditional spherical lenses introduce chromatic and geometric aberrations during imaging, limiting the field of view and imaging quality of AR glasses. The use of free lenses can eliminate or reduce these problems, thus improving the field of view and imaging quality of AR glasses. Additionally, free lenses can achieve precise control of light by adjusting surface shapes, resulting in better optical performance.