The PSD2 index of 3mm ultrathin large aperture optical components is difficult to converge effectively, which is influenced by various factors. In order to solve the problem, the measurement results of the PSD2 index were analyzed in two parts. One part was the results of the PSD2 index after removing the defocus and astigmatism, which we used to evaluate the impact of intermediate frequency errors. The other part was the surface shape PV value of the measurement area, which we used to evaluate the impact of low frequency errors. In the double-side polishing stage, the oscillating smooth polishing technology was used to smooth intermediate frequency errors of the optical surface, which eliminated the fine ripples in the PSD2 processing results. The surface shape local correction technology was used to improve the surface shape PV value of the measurement area. Through the synchronous control of the intermediate frequency and low frequency errors, the PSD2 index control for the whole surface of the optical components was realized. The RMS value of the the PSD2 index was converged from 1.38nm to 0.70nm on average.
With the increasing energy of high power laser devices, the laser-induced damage of optical components, especially fused quartz components, has become one of the core problems in the development of high power laser devices. Studies show that pure fused quartz glass has a high intrinsic damage threshold, but fused quartz glass will inevitably introduce a large number of subsurface damage during the process of grinding and polishing, and these subsurface damage is one of the important factors leading to the decline of laser damage resistance of optical components. It is of great significance to study the subsurface damage of solid abrasive for improving the damage resistance threshold of optical components. In this experiment, 3M's abrasive pad is used as a solid abrasive. The subsurface damage of fine grinding elements are directly observed and analyzed by combining HF pickling and optical microscopy. The results show that various subsurface damage can be detected by optical microscopy after HF pickling. Profilometer is used to measure the surface roughness of the sample, the comparative analysis of the subsurface damage of the fine grinding elements shows that the elements with solid abrasive lapping have smaller roughness when the abrasive size is the same, which has a shallower depth of subsurface damage layer correspondingly.
We present a method of using computer-generated hologram (CGH) to measure the radius of curvature of large
aperture long-focal-length lens. In this method, a large aperture transmission CGH is used as a transmission sphere to
generate the test and reference wavefronts by means of diffraction. To verify the feasiblity of this method, a 450 mm ×
450 mm transmission CGH is designed and fabricated for measuring the radius of 440 mm × 440 mm spatial filter lens.
Experimental results and error analysis show that the CGH test method features high accuracy and good repeatability.
This article mainly take the research on the technique of fabricating a steep off-axis aspherical mirror based on infrared interferometric testing. In the stage of asphercal shape grinding ,we take use of an infrared interferometer to test the aspherical surface error rapidly, along with the arm-swinging polishing method and choose the appropriate processing parameters according to the testing results. After more than twenty times polishing and testing circles ,the off-axis mirror’s wavefront error converge to PV≤5 λ,RMS≤1 λ(λ=632.8nm),this surface map is suitable for the final sub-surface polishing. Through these research and experiments, we have verified the applied advantage of infrared interferometric technique in fabricating steep off-axis aspherical mirror. This technology is also very useful in the processing other types of large-scale aspherical mirrors.
The ghost reflections can cause spurious fringes in the interferograms and lead to error in the measurement. So it is necessary to evaluate the influence of the ghost reflection spot for a correct interpretation of interferograms. In this paper, the ghost reflections of testing long focal length lens with computer-generated hologram (CGH) are investigated and geometrical model is established to obtain an expression for the size of the ghost reflection spot. Moreover, simulations and experiments are carried out by studying the ghost reflections of the long focal length lens in Shenguang III system.
A method for measuring the wavefront of wedged focus lens by using the Fizeau interferometer with large aperture and a reflective computer generated hologram (CGH) is proposed. The CGH has 6 zones: one main zone for the null testing of wedged focus lens, one additional zone for alignment the CGH substrate with the interferometer, and four others for the pre-alignment of wedged focus lens by projecting four marks. CGH design process was performed, including the ray trace model for multizone CGH and the optical testing configuration. Simulation results show that the desired precision can be reached with use of CGH and confirm the feasibility of this measurement method.
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