A 3 kHz High-Frequency Vibration Mirror Based on Resonant Mode

  • Weiqiang Han
Keywords: Vibration Mirror, Natural Frequency, Amplitude, Damping Ratio, Drive Coil, Moving Magnet

Abstract

Infrared small/weak target detection systems detect small/weak target by subtracting the strong atmospheric
background from the acquired image, in which a modulation process involving high-frequency vibration mirror
(VM) is required. VM is also an indispensable core component in some laser scanning applications requiring
extremely high accuracy. None of the existing VMs meet the requirements of large aperture and high frequency at
the same time. This study deals with the development of a method to generate high-frequency vibration for
large-aperture VMs, based on which a double torsion bar double moving magnet vibration mirror (DDVM) was
designed. Two mathematical models based on DDVM, namely free vibration model and stimulated vibration
model, are established, and then the conditions for achieving high frequency and large amplitude are obtained.
Furthermore, a method for simulating and correcting the influence of the static magnetic attraction on the mirror
surface shape is developed through a simulation of the designed DDVM based on the DDVM models, and a
method for calculating the damping and driving force amplitude using the measured vibration bandwidth of
DDVM structure is developed through dynamics simulation. Experimental results show that for a mirror with an
optical aperture of Φ40×56 mm, the optical scanning range reaches 0.584°, and the vibration frequency reaches
3,033 Hz. The acceleration resulting from such vibration amplitude and frequency of the VM with the above
aperture is more than 100 times the acceleration in rocket launch, which is difficult to achieve with other methods.
The measured frequency is very close to the simulation result (3075 Hz) and the frequency calculated using the
mathematical model (3098 Hz). The errors less than 2% prove the correctness of the DDVM mathematical model
and the simulation analysis. From experimental data, the calculated bandwidth Δf of DDVM is 6.1 Hz, the
maximum gain coefficient Gn is 37694.7 rad∙Hz2∙N-1, and the damping coefficient D is 2.87×10-4 kg∙m2∙s-1.
Thus, the accurate differential equation and the structure transfer function of DDVM are obtained.

Published
2020-04-01