Designing Micromachined Accelerometers with Interferometric Detection

Abstract

This paper explores designs for the implementation of high sensitivity accelerometers based on Fabry-Pérot Interferometers. Although such structures have the potential to achieve µg resolutions, design and implementation challenges can be limiting. This paper discusses the creation of such devices using two distinct proof mass and optical designs: one of a monolithic flexure with a thin film metallic reflector and another of an elastomeric flexure with a thin film multilayer dielectric reflector. Each device was fabricated, tested and characterized and conclusions about the advantages and disadvantages of the different design features are presented.

Optical Interferometric MEMS Accelerometers

“…For free-space FP accelerometers, Perez and Eklund et al designed a high-resolution micromachined accelerometer (Figure 6a) that achieved a bandwidth of 1 kHz and a resolution of 2.4 ng, based on the optimization of the relevant factors such as noise, reflectivity, surface roughness, and parallelism that affect the performance of FP MEMS accelerometers. [24][25][26][27] Zhao et al adopted 3D printing technology to fabricate an integrated FP MEMS accelerometer [15] and then optimized the crosssensitivity of the sensing structure (Figure 6b)to 0.004%. [28] To reduce the noise of the accelerometer, the team systematically analyzed the primary noise sources of the accelerometer and reduced the sensor noise from 11 μg Hz −1/2 to 330 ng Hz −1/2 through the modulation and demodulation techniques.…”

“…designed a high‐resolution micromachined accelerometer ( Figure a) that achieved a bandwidth of 1 kHz and a resolution of 2.4 ng, based on the optimization of the relevant factors such as noise, reflectivity, surface roughness, and parallelism that affect the performance of FP MEMS accelerometers. [ 24–27 ] Zhao et al. adopted 3D printing technology to fabricate an integrated FP MEMS accelerometer [ 15 ] and then optimized the cross‐sensitivity of the sensing structure (Figure 6b)to 0.004%.…”

Accelerometers

“…If the proof mass is opaque to the incident light (Figure 25(b)), the reflected light from the FPI will be picked up by a photodetector (Baglio et al 2004). If the proof mass is transparent to the source light (Figure 25(c)), the transmitted light will be collected to calculate the acceleration (Perez et al 2005). The horizontal surfaces can be made extremely flat, and multilayer antireflection and high-reflection coatings can also be easily applied.…”

A Novel Piezoresistive Accelerometer with SPBs to Improve the Tradeoff between the Sensitivity and the Resonant Frequency

“…However, these methods depend on new processes or new materials, and they are difficult to manufacture in mass production. Therefore, many researchers are still concentrated on the geometry design to optimize accelerometers [ 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 ].…”