Experimental research of the deterministic controlling process of surface figure in the large-aperture annular polishing

The response characteristics of the pitch polishing pad under the pressure of conditioner is the key factor which affect the control efficacy of surface figure in annular polishing. The effect of the environmental temperature and humidity, rotation speed of the pad, uploading ratio and eccentricity of the conditioner on the response characteristics of pitch polishing pad were experimental researched. To this aim, a control system of the environmental temperature and humidity on the 2.8m-aperture annular polishing machine is established. The control precision of the local environmental temperature upon the pad is up to ±0.1℃, and the control precision of humidity is up to ±1% RH. The experimental results indicate that the matching degree of the pad and the conditioner decides the changing rule of the surface figure of workpiece with the eccentricity of the conditioner. The new adjustable parameters including the environmental temperature and humidity and the uploading ratio of the conditioner were introduced to change the matching degree and improve the controllability of the of the surface figure. Under the optimized process, the long-term stability of the surface figure of the meter-scale optical element is realized using the 2.8m annular polishing machine, which is an important step for the final realization of the deterministic processing in the large-aperture annular polishing.