Cyclic Common-path Point-diffraction Interferometer Based On Fourier-transiorm Method

The optical wavefront measurement technology, widely applied in the adaptive optics,optical detection and so on, has played a tremendous role in the development of relatedwavefront detection technology. The point-diffraction interferometer (PDI), whichgenerates the standard wave as the reference wave by pinhole diffraction, can supplyeffective solutions for achieving high-precision optical detection. However, thecommon-path PDI holds some drawbacks in difficulty of phase shifting or wavefrontextraction, poor craft of making the PDI mask, poor real-time measurement, and low fringevisibility. A new-type cyclic common-path PDI will be researched to overcome severalabove limitations.The paper has developed a cyclic common-path PDI based on Fourier-transformmethod. It uses the polarization splitting cyclic path system to divide the incident linearpolarized light under test into two orthogonal linear polarized beams which propagate inthe opposite directions and along the same optical path. In this cyclic system, two positivelenses with the same focal length and a pinholed polarizer placed in the focal plane areused to gain reference and test waves. Linear phase modulation between reference and testwaves is introduced by titling the polarization beam splitter to obtain a carrier frequencyfringe pattern. Then the wavefront phase to be measured is reconstructed with theFourier-transform method. In addition, two key parameters affecting the accuracy ofwavefront reconstruction, i.e., the fringe visibility and carrier frequency, are deeplyanalyzed in the paper. Simulated and experimental results show that this system holdssome advantages, such as a simple and compact structure, easily debugging, adjustablefringe visibility and carrier frequency as well as real-time wavefront detection.The field of high-power laser transmission and control will often confront theirradiance scintillation. The performance of traditional wavefront sensors applicated inwavefront detection under the appearance of irradiance scintillation would seriouslydecline. Through numerical simulation, the paper analyzes the influence of irradiancescintillation to PDI pinhole filtering and production of reference wave. The results indicatethat, when the pinhole diameter is equal to half of the Airy diameter produced by anunberrated optical system, the effect on pinhole filtering in the case of the irradiance scintillation exists or not is rather little and high-precision reference wavefronts whoseroot-mean-square errors are less than0.05λ can be produced. The research results showthat the designed PDI system can well be applied in the wavefront detection underirradiance scintillation, and PDI will have a more wide space of application anddevelopment.