Analysis of capacitive sensing for 2D-MEMS scanner laser projection

Wantoch, Thomas von; Mallas, Christian; Hofmann, Ulrich; Janes, Joachim; Wagner, Bernhard; Benecke, W.

doi:10.1117/12.2038606

Cited by 3 publications

(3 citation statements)

References 3 publications

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“…For example, work [1] demonstrates an electrostatic micromirror, which possesses symmetric combfingers around the mirror plate applying one side for actuating and the other side for sensing the mirror position. The used capacitive principle enables not only the monolithic integration in one electrostatic device but also the usage by hybrid integration in MEMS devices of other actuation principles.…”

Section: State Of the Artmentioning

confidence: 99%

A study of integrated position sensors for PZT resonant micromirrors

et al. 2015

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PZT driven resonant micromirrors offer advantages of large scan angles and decreasing power consumption due to the benefits of resonant driving and high torque delivered by PZT actuators. Therefore they are entering into different application fields recently, for example as laser projection or head-up displays. For many uses position sensing of the micromirrors is necessary to set up closed loop controls. Thus, the development of integrated position sensors is aimed in this work. Investigation and evaluation of different position sensing principles have been performed. In previous works 1D and 2D PZT driven resonant micromirrors have been presented, which feature various spring suspensions and thinfilm PZT actuators as drivers. Due to the considerably different motion modes and resonant frequencies, which vary from 100 Hz up to 64 kHz, various position detection methods have been investigated. This work presents primarily fabrication and characterization results of the position sensors based on the direct piezoelectric effect, which will be compared to the position sensors using metallic strain gauge realized by the same fabrication technology. Analyses of the sensitivity, linearity and dynamic behavior of the sensors have been performed, by means of comparing the sensor signals and the micromirror position signals measured by a Position-Sensitive-Device. Advantages and drawbacks of the sensors are discussed and methods for eliminating the drawbacks are proposed

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Section: State Of the Artmentioning

confidence: 99%

A study of integrated position sensors for PZT resonant micromirrors

et al. 2015

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“…C. Tsai et al reported a biaxial electromagnetically driven piezoresistively sensed scanning micromirror fabricated in a CMOS process, but this method required considerable space in the MEMS micromirror system [ 11 ]. To realize a miniaturized monitoring scanning micromirror system, Hung et al reported a capacitively transduced, closed-loop controlled scanning micromirror with shared comb electrodes for driving and sensing [ 15 ], but using shared electrodes for the slow-axis trajectory control produced instability due to the nonlinearity from electrostatic transduction [ 16 ]. M. Lee et al examined a capacitive sensing strategy to quantify the shift between nominal and actual phase delays in the X and Y axes of a 2D electrostatic MEMS scanner [ 17 ].…”

Section: Introductionmentioning

confidence: 99%

Development of an Optoelectronic Integrated Sensor for a MEMS Mirror-Based Active Structured Light System

Cheng

Liu

et al. 2023

Micromachines

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Micro-electro-mechanical system (MEMS) scanning micromirrors are playing an increasingly important role in active structured light systems. However, the initial phase error of the structured light generated by a scanning micromirror seriously affects the accuracy of the corresponding system. This paper reports an optoelectronic integrated sensor with high irradiance responsivity and high linearity that can be used to correct the phase error of the micromirror. The optoelectronic integrated sensor consists of a large-area photodetector (PD) and a receiving circuit, including a post amplifier, an operational amplifier, a bandgap reference, and a reference current circuit. The optoelectronic sensor chip is fabricated in a 180 nm CMOS process. Experimental results show that with a 5 V power supply, the optoelectronic sensor has an irradiance responsivity of 100 mV/(μW/cm2) and a −3 dB bandwidth of 2 kHz. The minimal detectable light power is about 19.4 nW, which satisfies the requirements of many active structured light systems. Through testing, the application of the chip effectively reduces the phase error of the micromirror to 2.5%.

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“…Other techniques, such as electromechanical frequency modulation [7] and electromechanical amplitude modulation [8], are hampered by large size, limited bandwidth, and low signalto-noise ratio in their conventional implementations. Previous two-axis combdrive motion sensors [9] are able to monitor two axes of motion by sensing on one side of each axis.…”

Section: Introductionmentioning

confidence: 99%

Integrated Amplitude and Phase Monitor for Micro-Actuators

2022

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Micro-actuators driven on resonance maximize reach and speed; however, due to their sensitivity to environmental factors (e.g., temperature and air pressure), the amplitude and phase response must be monitored to achieve an accurate actuator position. We introduce an MEMS (microelectromechanical system) amplitude and phase monitor (MAPM) with a signal-to-noise ratio of 51 dB and 11.0 kHz bandwidth, capable of simultaneously driving and sensing the movement of 1D and 2D electrostatically driven micro-actuators without modifying the chip or its packaging. The operational principle is to electromechanically modulate the amplitude of a high-frequency signal with the changing capacitance of the micro-actuator. MAPM operation is characterized and verified by simultaneously measuring the amplitude and phase frequency response of commercial micromirrors. We demonstrate that the MAPM circuitry is insensitive to complex relationships between capacitance and position of the MEMS actuators, and it is capable of giving real-time read-out of the micromirror motion. Our measurements also reveal and quantify observations of phase drift and crosstalk in 2D resonant operation. Measurements of phase changes over time under normal operation also verify the need for phase monitoring. The open-loop, high-sensitivity position sensor enables detailed characterization of dynamic micro-actuator behavior, leading to new insights and new types of operation, including improved control of nonlinear motion.

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Analysis of capacitive sensing for 2D-MEMS scanner laser projection

Cited by 3 publications

References 3 publications

A study of integrated position sensors for PZT resonant micromirrors

A study of integrated position sensors for PZT resonant micromirrors

Development of an Optoelectronic Integrated Sensor for a MEMS Mirror-Based Active Structured Light System

Integrated Amplitude and Phase Monitor for Micro-Actuators

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