Empirical mode decomposition for self-mixing Doppler signals of hemodynamic optical probes

Pereira, Tânia; Vaz, Pedro G.; Oliveira, Tatiana; Santos, Inês; Pereira, Helena; Almeida, Vânia; Correia, C.M.B.A.; Cardoso, J. M. R.

doi:10.1088/0967-3334/34/3/377

Cited by 8 publications

(8 citation statements)

References 30 publications

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“…The STFT assumes that the signal is stationary during the analysis interval [7,14] and the overall spectrogram represents a sequence of spectral power distributions in a time versus frequency space. In specific cases, such as a not constant target velocity, the statistical distribution of the measured Doppler shifts is proportional to the power spectral density (PSD) of the target velocity.…”

Section: Self-mixingmentioning

confidence: 99%

“…This LD is extensively used in optical drivers, and all the system is based on simple electronic components with an optical scheme of a single optical axis [7].…”

Section: Technologymentioning

confidence: 99%

“…A constant current is imposed by a voltage regulator (LM337) in a configuration where a resistor ( ) sets the output current through the load. The electronic amplification circuit consists of an ultralow bias current monolithic operational amplifier (Texas Instruments, OPA129UE4) for the current-to-voltage conversion (trans-impedance amplifier) [7]. The acquisition box comprises a data acquisition system (DAS), a DC/DC converter, and an USB connection for primary power supply and interface with the host controller.…”

Section: Technologymentioning

confidence: 99%

“…The acquisition box comprises a data acquisition system (DAS), a DC/DC converter, and an USB connection for primary power supply and interface with the host controller. The DC/DC circuit converts the standard USB +5 V to the voltages required by the analog electronics (±15 V) of the optical probe [7].…”

Section: Technologymentioning

confidence: 99%

“…The information of the self-mixing signals is mostly encoded in the frequency domain and, to extract important data, signal processing techniques such as the Doppler spectrogram and power spectral density was used [7]. These methods allow the extraction of the movement profile and the absolute displacement.…”

Section: Introductionmentioning

confidence: 99%

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Submicron Surface Vibration Profiling Using Doppler Self-Mixing Techniques

et al. 2014

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Doppler self-mixing laser probing techniques are often used for vibration measurement with very high accuracy. A novel optoelectronic probe solution is proposed, based on off-the-shelf components, with a direct reflection optical scheme for contactless characterization of the target's movement. This probe was tested with two test bench apparatus that enhance its precision performance, with a linear actuator at low frequency (35 m, 5-60 Hz), and its dynamics, with disc shaped transducers for small amplitude and high frequency (0.6 m, 100-2500 Hz). The results, obtained from well-established signal processing methods for self-mixing Doppler signals, allowed the evaluation of vibration velocity and amplitudes with an average error of less than 10%. The impedance spectrum of piezoelectric (PZ) disc target revealed a maximum of impedance (around 1 kHz) for minimal Doppler shift. A bidimensional scan over the PZ disc surface allowed the categorization of the vibration mode (0, 1) and explained its deflection directions. The feasibility of a laser vibrometer based on self-mixing principles and supported by tailored electronics able to accurately measure submicron displacements was, thus, successfully demonstrated.

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Section: Self-mixingmentioning

confidence: 99%

“…This LD is extensively used in optical drivers, and all the system is based on simple electronic components with an optical scheme of a single optical axis [7].…”

Section: Technologymentioning

confidence: 99%

Section: Technologymentioning

confidence: 99%

Section: Technologymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Submicron Surface Vibration Profiling Using Doppler Self-Mixing Techniques

et al. 2014

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Novel Methods for Pulse Wave Velocity Measurement

2015

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The great incidence of cardiovascular (CV) diseases in the world spurs the search for new solutions to enable an early detection of pathological processes and provides more precise diagnosis based in multi-parameters assessment. The pulse wave velocity (PWV) is considered one of the most important clinical parameters for evaluate the CV risk, vascular adaptation, and therapeutic efficacy. Several studies were dedicated to find the relationship between PWV measurement and pathological status in different diseases, and proved the relevance of this parameter. The commercial devices dedicate to PWV estimation make a regional assessment (measured between two vessels), however a local measurement is more precise evaluation of artery condition, taking into account the differences in the structure of arteries. Moreover, the current devices present some limitations due to the contact nature. Emerging trends in CV monitoring are moving away from more invasive technologies to non-invasive and non-contact solutions. The great challenge is to explore the new instrumental solutions that allow the PWV assessment with fewer approximations for an accurately evaluation and relatively inexpensive techniques in order to be used in the clinical routine.

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Signal (Stream) synchronization with White noise sources, in biomedical applications

Vaz

Almeida

Ferreira

et al. 2015

Biomedical Signal Processing and Control

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When multiple acquisition systems are used to simultaneously acquire signals, synchronization issues may arise potentially causing errors in the determination of acquisition starting points and continuous clock offsets and shifts on each device. This paper introduces a processing method to efficiently synchronize these signals in the presence of white noise sources without the requirement of clock sharing or any other digital line exchange. The use of a signal source, such as white noise with a very wide frequency band, is of great interest for synchronization purposes, due to its aperiodic nature. This high bandwidth signal is simultaneously acquired by all the acquisition channels, on distinct systems, and, synchronized afterwards using cross-correlation methods. Two different correlation methods were tested; a global method, used when clock system frequencies are exactly known, and a local method, used when independent clocks evidence shifts over time that cumulatively account for long term acquisition errors in the synchronization process. In a computational simulation with known clock frequencies the results show a synchronization error of ≈1/10 of the time resolution, for both methods. For unknown clock frequencies, the global method achieved an error of 24/10 the time resolution, indicating a much poorer performance. In the experimental setup , only the local method was tested. The best result shows a synchronization error of 4/10 of the time resolution. All the signal conditioning and acquisition parameters were chosen taking into account potential biomedical applications.

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Empirical mode decomposition for self-mixing Doppler signals of hemodynamic optical probes

Cited by 8 publications

References 30 publications

Submicron Surface Vibration Profiling Using Doppler Self-Mixing Techniques

Submicron Surface Vibration Profiling Using Doppler Self-Mixing Techniques

Novel Methods for Pulse Wave Velocity Measurement

Signal (Stream) synchronization with White noise sources, in biomedical applications

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