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In order to solve the difficulties in testing surface of long focal length mirror using interferometer,a novel optical metrology using phase retrieval is developed.In this method,tested mirrors is illuminated by a coherent point light source,a series of diffraction intensity patterns near focus are collected,then phase retrieval algorithm reconstructs the surface error of tested mirror.Compared with interferometer,it simplifies the metrology setup and requires no special environment.Mathematic model of phase retrieval measurement is found according to diffraction theory,and is solved by iterative algorithm which derives from Gerchberg-Saxton algorithm.Validity of this method is tested by simulations and an experiment.A spherical mirror with curvature radius of 8 700 mm and diameter of 145 mm is tested using phase retrieval.The position of intensity patterns are corrected and appropriate patterns are chosen to be computed.The reconstructed result is correlated well with that tested by simultaneous phase-measurement interferometer.

This paper presents a novel structure for improving the stability and the mechanical noise of micromachined gyroscopes. Only one slanted cantilever is used for suspension in this gyroscope, so the asymmetry spring and the thermal stress, which most micromachined gyroscopes suffer from, are reduced. In order to reduce the mechanical noise, the proof masses are designed to be much larger than in most micromachined gyroscopes. The gyroscope chip is sealed at 0.001 Pa vacuum. A gyroscope sample and its read-out circuit are fabricated. The scale factor of this gyroscope is measured as 57.6 mV/(deg/sec) with a nonlinearity better than 0.12% in a measurement range of ±100 deg/sec. The short-term bias stability in 20 min is 60 deg/h.