Vari-focal holographic lens and its tunable performance

A vari-focal coaxial holographic lens-based photopolymer capable of pneumatic focal length tuning was developed. The lens utilizes the spatial dispersion characteristics of its diffraction spectrum to reflect the pneumatic adjustability. The linear dispersion range exceeds 60mm during the pneumatic zooming process. The tunable range of focal length expressed at 633 nm and the pressure sensitivity reach 60 mm and 10.942 mm/Kpa, respectively. The stable linear dispersion range ensures the high accuracy for confocal displacement sensing. The lens preserves axial dispersion sensitivity of 0.7 nm/mm during pressure adjustments. A rapid response with average actuation time of 27.59 ms was observed. The millisecond-scale response time and linear pressure sensitivity make it particularly suitable for dynamic measurement applications requiring rapid focal adjustments. The tunable lens is expected serve as a platform for next-generation tunable metrology devices for displacement and surface morphology measurements.