Motion analysis of Micro-electro-mechanical system (MEMS) is a powerful diagnostic tool enabling evaluation of the dynamic behaviour and the status of MEMS. A backscattering differential laser Doppler system is presented. The working principle and optical diagram of the system are explained in detail. In accordance with the characteristic of the measurement system, high-performance phase-locked loop is used to detect a weak measurement signal. Then measurement signal is transferred to computer and further analyzed there. Furthermore, a laser focusing method is described to improve the measurement. The focusing system is composed of a spatial filter and an aspheric lens C240TM-A, and focal spot size is less than 50 um. The silicon micromachined resonator is used as an example in experiments, and the resonant frequencies and the mean amplitude of MEMS are determined. Experimental results indicate that dynamic characteristics of MEMS can be measured well.
A optical measurement system of Micro-electro-mechanical system (MEMS) motion is demonstrated to increase the efficiency of MEMS design and manufacturing. The system is developed based on the heterodyne laser Doppler technology, and frequency shift of 40MHz is introduced by a Bragg cell. The paper introduced MEMS vibration theory, designed optical structure and electronic circuit, and obtained the linear relation between the Doppler shift and the target velocity. Experiments on driving and measuring double-ended tuning fork resonator were carried out. The resonator is driven by using electrostatic force at its natural frequency 2.4KHz. Experimental results indicate that the measure system can be used to measure MEMS motion with high accuracy.
The phase shifter is necessary in the optical phase-shifting measurement. At present the phase shifter commonly used is approximately divided into the penetrance-type and the reflection-type. In this paper, a reflection-type phase shifter made of piezoelectric ceramic stackup assemble is developed. The assemble are constituted of the flat piezoelectric ceramic with parallel connection circuit and inline structure. The communication between the computer and MCU is by RS232. The D/A converter controlled by the MCU outputs 0~10V voltage. Then the voltage is amplified to 0~400V DC voltage by the designed linear DC amplifier. When this voltage loads on the piezoelectric ceramic stackup assemble, the assemble will axially extend 0~5mm. In this paper, the connecting types for the mechanical construction and circuit of the piezoelectric ceramic stackup assemble, the driving power and the DC amplifier with high linearity are all introduced. The whole system developed is standardized by using phase-interfering Michelson. The standardization and the practical application indicates that this system has excellent linearity and precision repeatability.
For describing the micro-topography of a measured surface reasonably, this paper puts forward a parameter named minimal area of average height of the surface micro-topography based on the least square method, which is different from the qualitative uniformity surface parameters such as correlation theory, power spectral analysis, profile matrix spectrum and surface matrix spectrum. That means to look for the minimal size square which could represent the average height value of the sample area. If the deviation between the mean height values in this area and in the sample area is ±5% which is ±2σ of Gaussian distribution, and at the same time the ratio between the minimal area and the sample area is less than 0.8, then the measurement data from the sample area is considered as the characteristic of the measured surface micro-topography. Some standard samples finished by lapping grinding, surface grinding, planning, and end milling and plain milling are measured by using phase-shift Michelson and micro-grating-projection method in this paper. The two measurement principles are given in this paper. The Ra value of the standard samples measured and the measurement results of the minimal area of average height are given. The results shown that the parameter of minimal area of average height exist good consistency with the parameter of Ra.
In order to realize the coupling of the crystal spectrum line, the wavelength output by the laser-diode must be adjusted to be accordant with the peak value absorbed by laser crystal in the solid laser of the laser-diode pump. In this paper, the finite element analysis (FEA) of the heat emission of the to-3 encapsulated laser-diode was researched and an accurate PI+Fuzzy temperature control system was developed. The refrigeration and the accurate temperature control of the high-power laser-diode was realized by the semiconductor refrigerator. Combined with fussy control and PI control, a full solid refrigerator of the laser-diode was developed. AT89C51 MCU and CRI fussy control arithmetic were used in this system. So the system has high temperature control precision and little chatting. The rate of change of the optical power peak value output by the laser-diode was less than 1%.
To provide useful insight into the reliability of silicon micromachined resonator, a measurement system of resonator vibration is presented to check the dynamic characteristics of resonator. The system utilizes heterodyne laser Doppler techniques and acquires the relation between resonator motion and Doppler shift of scatter beam. The vibration principle of resonator was expatiated detailedly and a special driving control circuit was also designed. Experiments on driving and measuring double-ended tuning fork vibration were carried out. The frequency of driving signal is 2.4 kHz and the peak-to-peak value of driving voltage is 140 V. Experimental results indicate that the system can measure dynamic characteristics of Micro-electro-mechanical system (MEMS) well.