Real-time monitoring and control system of an industrial robot with 6 degrees of freedom for grinding and polishing of aspherical mirror
Aspherical mirrors have higher performance and lighter weight than spherical mirrors. However, it is not easy to process, measure, and evaluate their shapes. In particular, large aperture aspherical mirrors used in satellites require high precision and take a long time to process. The conventional process is machined using a computer numerical control with a gantry structure. However, there is a disadvantage that it is difficult to process complex shapes due to lack of degrees of freedom. In order to overcome these problems, we developed a shape processing system using an industrial robot with 6 degrees of freedom. The system consists of toolpath generation program, real-time robot monitoring, and control program. We have verified the performance of the developed system through simulation software provided by the robot manufacturer as well as actual robot operation.
Study on Precision Grinding of Micro Aspherical Surface (4th Report)
Needs of digital devices increase rapidly in recent years, and the demand for a micro axis-symmetric aspherical glass lens of large numerical aperture is expanding rapidly especially in that device. Moreover blue lasers have been increasingly used to make wavelengths short and the maximum tangent angle of the aspheric shape has increased. Therefore ultra-precision grinding technology of ceramic dies became to be a core technology. Authors have successfully developed the 45 degrees tilted grinding method, and ultra-precision micro aspherical shape has been obtained. The improvement of the form accuracy will be required because the specifications of micro lenses become more and more strict in future. However, the shape correction cannot be done satisfactorily, because the wheel wear is not equal and the grinding point on the wheel moves. In this paper, a new grinding method is proposed to solve the above problems. In this method, three-axes (X, Y, Z) are controlled simultaneously so that the position of the grinding point on the diamond wheel is fixed. Then the grinding system was developed and grinding experiments using micro symmetric aspherical dies of tungsten carbide were carried out.
Photoreflectance characterization of vanadium-doped GaAs layers grown by metalorganic vapor phase epitaxy
Abstract We characterized the vanadium-doped (GaAs:V) layers grown on GaAs substrate by metalorganic vapor phase epitaxy. The conductivity of the samples is checked by the Hall effect measurements, and it is n type with electrons concentration ranging from 2×10 13 to 2×10 17  cm −3 . We used the photoreflectance technique (PR) to study the effect of vanadium doping on the optical properties of GaAs. Our experimental results show that the built-in electric field F and the broadening parameter Γ 0 increase with V-doping concentration. Furthermore, the temperature dependence of the built-in electric field and the broadening parameter of GaAs:V samples have been investigated by PR. It has been observed that these parameters increase with increasing temperature. The decrease of the built-in electric field with decreasing temperature is due to the photovoltage effect.We characterized the vanadium-doped GaAs (GaAs:V) layers grown on GaAs substrate by metalorganic vapor phase epitaxy.