Lens Diameter
Lens diameter refers to the width of each individual microlens. While there’s no absolute physical limit to the diameter, practical design boundaries emerge from optical modeling and fabrication constraints.
Lower Bound Considerations:
When diameters approach ~10 µm, the system transitions from purely refractive behavior to a hybrid refractive-diffractive regime. In this zone, wave effects like diffraction become significant, necessitating more advanced modeling beyond traditional ray optics. Because of this, most MLA designs avoid sub-10 µm lens diameters unless specifically leveraging diffractive effects (e.g., in diffractive optical elements or hybrid structures).
Upper Bound Considerations:
There is no strict upper limit on diameter; however, as diameter increases, so must the lens sag (height), in order to maintain optical power. This introduces significant constraints on fabrication fidelity, material flow, and process repeatability—especially for replicated or lithographic microlens arrays.
Trade-offs:
Small (<20 µm): Enables dense packing, fine beam control, but suffers from increased diffraction. Large (>200 µm): Possible thermal effects due to high sag typically associated with large diameter.
