Abstract
This paper presents a flame retardant 4 (FR4)-based electromagnetic scanning micromirror, which aims to overcome the limitations of conventional microelectromechanical systems (MEMS) micromirrors for the large-aperture and low-frequency scanning applications. This micromirror is fabricated through a commercial printed circuit board (PCB) technology at a low cost and with a short process cycle, before an aluminum-coated silicon mirror plate with a large aperture is bonded on the FR4 platform to provide a high surface quality. In particular, an electromagnetic angle sensor is integrated to monitor the motion of the micromirror in real time. A prototype has been assembled and tested. The results show that the micromirror can reach the optical scan angle of 11.2° with a low driving voltage of only 425 mV at resonance (361.8 Hz). At the same time, the signal of the integrated angle sensor also shows good signal-to-noise ratio, linearity and sensitivity. Finally, the reliability of the FR4 based micro-mirror has been tested. The prototype successfully passes both shock and vibration tests. Furthermore, the results of the long-term mechanical cycling test (50 million cycles) suggest that the maximum variations of resonant frequency and scan angle are less than 0.3% and 6%, respectively. Therefore, this simple and robust micromirror has great potential in being useful in a number of optical microsystems, especially when large-aperture or low-frequency is required.
Highlights
The scanning micromirror is a promising component for wide applications, such as projection displays [1], barcode readers [2], micro-spectrometers [3,4] and biomedical imaging [5]
A prototype of flame retardant 4 (FR4)-based electromagnetic scanning micromirror integrated with an angle sensor is presented in this paper
The device has a large aperture (11.7 mm × 10.3 mm) with high surface quality and low frequency, which is difficult to achieve with the conventional silicon microelectromechanical systems (MEMS)
Summary
The scanning micromirror is a promising component for wide applications, such as projection displays [1], barcode readers [2], micro-spectrometers [3,4] and biomedical imaging [5]. A low-frequency scanning and large-aperture micromirror is required for a broad spectrum of applications, such as micro-spectrometers [4], laser projection [16,17,18], fluorescence microscopes [19] and so on. It has been a continuous and ongoing task to find a proper alternative in order to meet the vast application demand. A robust scanning micromirror can be quickly fabricated using FR4 as the substrate through the commercially available and low-cost PCB fabrication process
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