Method for fabricating small space period phase elements based on magnetorheological polishing

Abstract

Traditional optical processing technology is limited by factors such as the geometric size and stability of the removal function of the processing equipment, and it is very difficult to process optical elements with complex structures with large depths and small periods. In particular, the high-efficiency and high-precision processing of optical elements with complex structures whose depth is micron-level and space period is millimeter-level has always been a technical difficulty. This paper proposes a method for processing optical components with complex structures based on magnetorheological polishing technology, focusing on solving the traditional magnetorheological polishing technology small size removal function generation and stable control problems, and obtaining small size removal with stable removal efficiency and morphology function. The magnetorheological fluid circulation system is a key component of the magnetorheological polishing machine. The structure of traditional magnetorheological fluid circulation system is difficult to match the stable transmission of magnetorheological fluid under small flow conditions. This paper proposes a method of dual peristaltic pump & pulsation damper combined with variable-diameter back pressure pipeline to achieve the stability of magnetorheological fluid control. The flow fluctuation error of magnetorheological fluid is reduced from 10-40ml/min to 1-5ml/min. The diameter of the polishing wheel of the machine is 20mm and the flow rate of the magnetorheological fluid is 200ml/min. A two-dimensional sinusoidal surface processing was performed using magnetorheological machine. Sinusoidal surface design PV=1.0λ (λ=632.8nm), RMS=159.5nm, the space period is 3mm, the element size is 50mm×50mm. The width of removal function is 1.33mm, FWHH (Full Width at Half Height) is 0.98mm, and volume removal rate is 0.004mm 3/min. After the element is completed, the residual RMS is reduced from the original 159.5nm to 15.7nm, and its convergence rate is 90.1%, with high convergence accuracy. The experimental results show that the configuration of the magnetorheological fluid circulation system proposed in this paper realizes the generation and stable control of the small size removal function and finally realize the fabricating of phase components with a minimum space period of 3mm.