The finite-thickness model applied to designs of closed-boundary cylindrical microlenses with small f-numbers

Instead of the existing zero-thickness model (ZTM), the finite-thickness model (FTM) is employed to designs of closed-boundary cylindrical microlenses (CBCMs) with small f-numbers based on the wave-front interference principle. To demonstrate the superiority of the FTM to the ZTM in the design of CBCMs, focal performance of all the designed microlenses is investigated by the rigorous boundary element method (BEM). For CBCMs with small f-numbers, numerical results by the BEM reveal that the designed CBCMs by using the FTM possess better focal performance than the designed CBCMs by using the ZTM, such as a more exact real focal position, a smaller focal spot size, and a higher diffraction efficiency.