Abstract:High precision and areal measurement of the vibration modes of hemispheric shell resonator (HSR) is of great challenge. A novel measurement method is developed based on deflectometry. The measurement of vibration modes of HSR is converted into the measurement of swing angles of normal vectors. By the reverse ray tracing, a measurement system is designed. On the basis of the captured images of blurred spots, the swing angles of the normal vectors are decomposed into the latitude and longitude directions. Then, the parameters of vibration modes of HSR are calculated accordingly. Experimental results show that the method can achieve precise fitting of the vibration modes. The detecting sensitivities against the vibration amplitude and swing angle of the normal vector are 10 nm and 10 μrad, respectively. This measurement method has the advantages of simple and flexible structure and superior capability of anti-disturbance, thus it can find wide applications in various fields.