Hybrid defocus sensor with an enhanced dynamic range

Defocus is a major optical aberration affecting imaging and beam propagation across various fields. While existing measurement techniques often require complex wavefront reconstruction, modal wavefront sensors (MWSs) and astigmatic defocus sensors (ADSs) offer simpler, intensity-based methods but suffer from limited dynamic range. This study proposes a novel defocus sensing technique that combines MWS and ADS principles, using intensity measurements at just two defocus planes. The method enables fast, straightforward implementation with a significantly enhanced dynamic range. Theoretical analysis, supported by simulations, demonstrates its advantages over conventional sensors. An implementation strategy using computer-generated holography is also presented, with experimental and simulation results aligning well with theory.