Research On Diffractive Pyramid Wavefront Sensor

Adaptive optics system real-time measure and compensate the distortion caused by atmospheric turbulence. It improves the quality of beam propagation in the atmosphere and the imaging quality of the optical system effectively. Adaptive optics techniques changes the situation that the traditional optical techniques is helpless on the interference. The distortion of the wave-front can be real-time measured by wave-front sensor and the corrected signal can be also given to the corrector according to it. Wavefront sensor is requried with high speed, high precision and the ability of detecting in the weak light at the same time. Usually, shark-hartmann wavefront sensor (HSWFS) is limited by the detection ability in weak light and spatial sampling rate. Pyramid wavefront sensor (Pyramid wavefront sensor, PWFS) is superior to shark-hartmann wavefront sensor on the above two aspects. At present, most of the pyramid wavefront sensor is refractive. The standard internationally recognized of pyramid mirror processing is the root mean square value of the surface shape error is smaller than twenty percents of the wavelength, the width of the platform is less than ten percents of the diameter of the airy disk. It is difficult for the domestic traditional optical polishing method and LIGA (Lithography, electroplating (German:Galvanik) and molding (German:Abformung)) method to produce a pyramid meets the precision. The accuracy of measurement reduces due to the roofs existing on its vertexes and platform.A kind of diffractive pyramid wavefront sensor for the measurement of wavefront aberration is designed based on the refractive pyramid wavefront sensor and the binary optical principle. The theoretical derivation of diffractive pyramid wavefront detection is made. The ablity of diffractive pyramid wavefront detection is calculated. The experments are also done. The experments results meet calculation results well and show that the diffractive pyramid wavefront sensor is capable of detecting the wavefront aberrations effectively and it can build miniature measurement system.First of all, a diffraction pyramid wavefront sensor(DPWFS)is designed based on the refraction pyramid wavefront sensor, micro optical machining technology and the binary optics in this paper. It solves the problems of refractive pyramid wavefront sensor in optical processing. It provides a feasible way to abtain a compact, easy processed pyramid wavefront sensor with high measurement precision.And then, the theoretical derivation of diffractive pyramid wavefront detection is made. The ablity of diffractive pyramid wavefront detection is calculated in detail. The simulation results show that the detecting capabilities of diffractive pyramid wavefront sensor is close to these of refractive one. It can be applied to the actual measurement of wave front.Next, the reconstruction algorithm of diffractive pyramid wavefront sensor is analyzed. The reconstruction results are abtained based on the model method. The recovery results confirm the validity of the recovery algorithm.Finally, the diffractive pyramid wavefront sensor is made and measurement experiment system is set up based on a liquid crystal spatial light modulator (LC-SLM)to study the detection ability of diffractive pyramid wavefront sensor to static wavefront aberration. The experimental results verify the diffractive pyramid is capble to be applied in adaptive optics system, especially the tiny feasibility adaptive optics system.