Refractive Index Measurement With High Precision by a Laser Diode Self-Mixing Interferometer

Chen, Chenxi; Zhang, Yongbing; Wang, Xiulin; Wang, Xiaozhong

doi:10.1109/jphot.2015.2431256

Cited by 9 publications

(3 citation statements)

References 17 publications

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“…The SMI effect in LDs could also be employed as a simple translation technique to measure the optical phase shift as a function of the moving distance of the sample [22]. The refractive index could be determined by analyzing the fringe number of the SMI signals with respect to the sample's moving distance and the angle of incidence [23]. An experimental accuracy of 0.004 is achieved.…”

Section: Introductionmentioning

confidence: 99%

Enhanced Vibration Measurement through Frequency Modulated Laser Diode Self-Mixing Interferometry

Liao,

Chen,

Hsiao

2024

Preprint

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Self-mixing interference (SMI) has emerged as a powerful non-contact vibration sensing technique, leveraging the inherent coupling between laser emission and external optical feedback. However, conventional SMI systems often face limitations in signal resolution and measurement accuracy, particularly when probing low-amplitude vibrations or low-reflectivity targets. This study proposes a novel frequency modulation (FM) approach, FM-SMI, to enhance the capabilities of SMI setups. By intentionally modulating the laser frequency of 20 kHz, the FM-SMI technique induces a segmentation of the interference signal, effectively increasing the temporal resolution and facilitating the detection of finer vibration details. Comprehensive experiments involving oscillating speakers and rotating silicon wafers validate the superior performance of the FM-SMI system. Notably, the frequency-modulated signals exhibit stability and robustness, even under low-amplitude vibration conditions or when targeting low-reflectivity surfaces. The enhanced signal quality, coupled with numerical processing techniques, enables precise extraction of vibration characteristics, including amplitude variations and surface topographies. The proposed FM-SMI approach demonstrates its potential as a versatile tool for high-precision, non-contact vibration measurements across diverse applications, such as, non-destructive testing and the characterization of vibration induced by the rotational systems.

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Section: Introductionmentioning

confidence: 99%

Enhanced Vibration Measurement through Frequency Modulated Laser Diode Self-Mixing Interferometry

Liao,

Chen,

Hsiao

2024

Preprint

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“…Among the several applications of SMI that have been demonstrated, in this paper, we focus exclusively on the measurement of vibrations, that is, periodic (and most frequently) sinusoidal small movement of the target. We will not treat other self-mixing measurements or applications like, for example, displacement [5][6][7][8], distance [9,10], velocity and flow rate [11,12], planarity [3], angle [13][14][15], physical quantities (thickness and index of refraction [16,17], linewidth [18], and alpha-factor [19]), the use of self-mix as a detector of optical echoes [20,21], or consumer applications like scroll [22] and gesture AR/VR [23] sensors. The interested reader may also consult general reviews [24] and tutorials like those provided by Refs.…”

Section: Introductionmentioning

confidence: 99%

Vibration Measurements by Self-Mixing Interferometry: An Overview of Configurations and Benchmark Performances

Donati

2023

Vibration

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Self-mixing interferometry (SMI) is suitable to sense and measure vibrations of amplitudes ranging from picometers to millimeters at frequencies from sub-Hz to MHz’s. As an optical probe, SMI has the advantage of being non-invasive with the ability to measure without any treatment of the target surface and operate from a substantial standoff distance from the target. As an additional advantage, the SMI configuration is much simpler than that of conventional interferometers as it does not require any optical part external to the laser source. After a short introduction to the basics of SMI, we review the development of configurations of SMI instruments for vibration measurements, based on both analog and digital processing, with record performance to cover the range of vibration amplitudes from 0.1 nm to 1 mm, frequencies up to MHz, and stand-off distances up to 100 m. These performances set a benchmark that is unequaled by other approaches reported so far in the literature. The configurations we describe are (i) a simple MEMS-response testing instrument based on fringe counting, (ii) a half-fringe locking vibrometer for mechanical mode analysis and transfer function measurements, with a wide linear response on six decades of amplitude, (iii) a vibrometer with analog switching cancellation for μm-to-mm amplitude of vibrations, and (iv) a long standoff distance vibrometer for testing large structures at distances up to 100 m and with nm sensitivity. Lastly, as the vibrometer will almost invariably operate on untreated, diffusing surfaces, we provide an evaluation of phase-induced speckle pattern errors affecting the SMI measurement.

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“…aser feedback based self-mixing interferometry (SMI) [2,3] has been demonstrated for multiple sensing applications such as velocity [4], displacement [5,6], distance [7], vibration [8], flow [9], tomography [10], 3D imaging [11], angle [6], and refractive index [12] etc. As opposed to conventional two-beam interferometry, SMI enables a compact, self-aligned and lowcost metric sensor (see Fig.…”

Section: Introductionmentioning

confidence: 99%

High Resolution Laser Self-Mixing Displacement Sensor Under Large Variation in Optical Feedback and Speckle

et al. 2020

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Self-Mixing interferometry (SMI) signal characteristics are highly dependent on both the operating optical regime and target surface. In this paper, a method is proposed to overcome some identified limitations of the even power scalable algorithm (EPSA) [1], such as the required operating regime to be weak feedback. In addition, by using the up-sampling techniques, the number of stages involved in the even-power scalable algorithm can be drastically increased without any data acquisition bandwidth modification. Here, 10 successive stages have been successfully implemented to achieve a theoretical resolution of λ0/2 13. It is further shown that the proposed method can handle and process weak, moderate and strong feedback regime as well as speckle affected SMI signals more efficiently. Lastly, FPGA based hardware emulation of EPSA is also done for later embedded implementation of this high-resolution algorithm. FPGA synthesis results show that the designed system can measure maximum target velocity up to 1.18 m/s while consuming total power of 1.4W.

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Refractive Index Measurement With High Precision by a Laser Diode Self-Mixing Interferometer

Cited by 9 publications

References 17 publications

Enhanced Vibration Measurement through Frequency Modulated Laser Diode Self-Mixing Interferometry

Enhanced Vibration Measurement through Frequency Modulated Laser Diode Self-Mixing Interferometry

Vibration Measurements by Self-Mixing Interferometry: An Overview of Configurations and Benchmark Performances

High Resolution Laser Self-Mixing Displacement Sensor Under Large Variation in Optical Feedback and Speckle

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