| This paper bend on the research work of how to optimize the wavefront correcting method of an adaptive optics, it includes several parts.(1) Primary theory of wavefront correction of adaptive opticsBegin with the wavefront detecting, the theoretical scheme of Hartmann-Shack (H-S) wavefront sensor was introduced; several zonal wavefront reconstruction methods and wavefront solutions which could match various restricting conditions were compared. Wavefront decomposing and the modal wavefront reconstruction methods were analyzed. The basic procedure of adaptive optics was introduced.(2) The maximum measurable range and measurement precision of H-S wavefront sensorThe maximum measurable range of H-S wavefront sensor is determined by the structural parameters of itself. A deformable mirror must correct the deformation of itself before it could correct other one, therefore the maximum measurable range of a wavefront sensor must match the performance of the deformable mirror.The measurement precision of H-S wavefront sensor is closely related to the size of subaperture beam spot, the number of pixels in one subaperture, beam intensity, the A/D precision of the CCD output signal. When the beam intensity is relatively high, it is not necessary for you to use many pixels in order to acquire high measurement precision. When the beam intensity is weak, the measurement precision could be improved by using more pixels in one subaperture, enlarge the amplify coefficient of the CCD very front signal, and improve the A/D precision of CCD output signal when the electronic noises are relatively low.(3) Study of the data precision of wavefront-reconstruction-matrixThis part applies the Southwell zonal wavefront reconstruction model to some terms of Zernike polynomials by numeric simulation, and the errors caused by data precision of wavefront-reconstruction-matrix is studied. The relative errors do not exceed 1.0% before the sixth term of Zernike polynomials when the reconstruction-matrix is memorized in 8Bit data precision, and more precise data types can not reduce the errors about the next several terms of Zernike polynomials. Ameasured wavefront is also studied, the result comes to the same.(4) Morbidity study of wavefront-reconstruction-matrix influenced by subaperture partition mannerHow to optimize the subaperture partition manner is the research focus of this part. Zonal wavefront reconstructing model is adopted, the least-squares solution is applied, and the condition number of wavefront-reconstruction-matrix is used to estimate how its morbidity is. The computer simulation results indicate that the number of subapertures mainly influences the morbidity. Appropriate manner of subaperture partition may greatly decrease the degree of the morbidity. When the appropriate number of subapertures is selected, the size variation of the subaperture will make rather small influences to the degree of the morbidity when the variation is rather small. When both the appropriate number and size of subapertures are selected, the collimating displacement and rotating displacement will also only make small influences to the degree of the wavefront-reconstruction-matrix morbidity.(5) Primary study of an adaptive optics system based on a personal computerA 52 units adaptive optics system was built. The system's high frame-rate wavefront sampling card, subaperture's wavefront slope calculating module, wavefront reconstruction module, the control arithmetic module, as well as the digital output port were totally based on a personal computer. The system's "0" seeking experiment was taken on this platform, and the results were relatively good.The research results of the several foregoing parts were taken into account in the system's study procedure. The wavefront-reconstruction-matrix was memorized in 8Bit data precision. A proper subaperture partition manner was adopted. Some truths during the experiment procedure fully demonstrate that an adaptive optics system with an improper subaperture p... |
PDF Full Text Request