Fourier transform infrared spectrometer based on an electrothermal MEMS mirror

Abstract

This paper presents a micro Fourier transform infrared spectrometer (μFTIR), enabled by an H-shaped electrothermal microelectromechanical systems (MEMS) mirror. A special driving method was developed for obtaining a linear, uniform-speed motion of 186 μm, and the tilting angle of the MEMS mirror was as small as 0.06°, so there was no need of complex closed-loop control. A telecentric lens was employed in the interferometer of the μFTIR to reduce the influence of the MEMS mirror tilting effect. Also, a new phase interpolation algorithm, instead of the traditional fringe interval method, was applied in the process of the spectral reconstruction to improve the spectral stability. Finally, the new μFTIR was applied in the composition prediction of soybeans, and the experimental results show that it can accurately measure grain moisture, protein, and fat contents.

Nondestructive On-Site Detection of Soybean Contents Based on An Electrothermal MEMS Fourier Transform Spectrometer

“…1(a), the fixed mirrors in the DMI are all placed on the same side to simplify the assembling process. Although the DMI configuration is similar to the one previously reported in [22], this DMI has a more compact structure and the size of the optical core is only 50 mm × 30 mm × 27 mm, which is reduced by a factor of 4 from that in [22]. The optical design of the double lenses is optimized using Code V [25] and is presented in Fig.…”

“…By calculating the root mean square (RMS) of prediction error between the chemical values and prediction values, the regression model was obtained by the best regression coefficients corresponding to the minimum RMS of the prediction error. More details about building the prediction model can be found in [22]. Fig.…”

“…Compared with electrostatic and electromagnetic actuators, electrothermal bimorph actuators have a clear advantage of large linear scan range without the need of complex resonance operation [21]. By using a properly tuned driving setting and a phase interpolation algorithm, large piston and small tilting angle without closed-loop control are simultaneously achieved with such electrothermal MEMS mirrors [22]. Several μFTIR systems based on the electrothermal MEMS mirrors have been demonstrated [23], [24].…”

Stability Study of an Electrothermally-Actuated MEMS Mirror with Al/SiO2 Bimorphs

“…Electrothermal actuation based on thermal bimorphs has been widely applied on scanning microelectromechanical systems (MEMS) mirrors due to its advantages of large displacement, high fill factor, and economical fabrication process [1]. Thermal bimorphs refer to cantilever beams composed of two structural layers with different thermal expansion coefficients (TECs).…”

“…Aluminum and Al/SiO2 are the most frequently-used bimorph materials as they are common materials in semiconductor fabrication and their TEC difference is large. Al/SiO2 electrothermal bimorph-based MEMS mirrors have been extensively studied [2], and have also been used in many applications, such as endoscopic optical imaging [3] and microspectrometers [1]. However, feedback control is often needed for electrothermal MEMS mirrors in high-precision applications because of the relatively low repeatability and stability of Al/SiO2 bimorph actuators [4].…”