Improvement of optical resolution and mechanical robustness for near-field recording system

Near-field optics applied annular aperture technique is optimized to improve near-field optical imaging performance. By introducing an annular aperture that has three annular zones with binary transmittance and different phase retardation, decreased focused spot size, reduced sidelobe intensity and extended focal depth are achieved. In addition, through the development of novel near-field air-gap control algorithm, near-field recording system, which inevitably maintains extremely small air-gap, becomes much stable with the enhanced robustness for external shock and vibration.