A digital signal processing module for real-time compensation of nonlinearity in a homodyne interferometer using a field-programmable gate array

Kim, Jong-Ahn; Kim, Jae Wan; Kang, Chu-Shik; Eom, Tae Bong; Ahn, Jin Ho

doi:10.1088/0957-0233/20/1/017003

Cited by 28 publications

(20 citation statements)

References 7 publications

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“…It is compensated by fitting the phase quadrature signals of the interferometer using the least square method. It is a time-consuming process; it should be implemented in offline mode (Keem et al, 2005;Kim et al, 2009;Ye et al, 2014Ye et al, , 2015. In the optical encoder, the position is determined with sinusoidal signals using amplitude to phase converter.…”

Section: Linearization Of the Optical Sensorsmentioning

confidence: 99%

Linearization of the sensors characteristics: a review

Islam¹,

Mukhopadhyay

2019

International Journal on Smart Sensing and Intelligent Systems

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Today, the sensing devices play an important role for various system automation and monitoring of different physical and chemical parameters. Nonlinearity is an important long-time issue for most of the sensors, so to compensate nonlinearity, various linearization schemes are reported in the literature. The accuracy of linearization schemes depends on the type and the nonlinearity value of the sensor output. Since it is difficult to find an exact polynomial equation or other functions to represent the response curve; it gives more error when the measurement parameter is determined from the inverse approximation functions. As many sensors are used for different applications, the linearized characteristics will simplify the design, calibration, and accuracy of the measurement. This paper presents a review of different methods applied to linearize sensor characteristics reported in the literature. Due to availability of high-performance analog devices, analog methods are still popular among many researchers. However, due to the advancement of IC technologies, hardware implementation of the software methods can be done easily with reduced time, cost, and more accuracy, so the digital methods combined with software techniques perform the job with better flexibility and efficiency.

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Section: Linearization Of the Optical Sensorsmentioning

confidence: 99%

Linearization of the sensors characteristics: a review

Islam¹,

Mukhopadhyay

2019

International Journal on Smart Sensing and Intelligent Systems

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“…There are two common ways to correct or compensate the periodic error to achieve more precise measurement: 1) design a novel optical configuration that eliminates the periodic error inherently [10,11,12,13,14], and 2) use a compensation algorithm applied to the measurement data to correct the periodic error electronically [15,16,17,18,19,20,21,22,23,24]. A novel optical configuration of interferometer would lead vastly large and complicated setup, and be more sensitive to environment.…”

Section: Periodic Errormentioning

confidence: 99%

Real-time FPGA-based Kalman filter for constant and non-constant velocity periodic error correction

Wang

Burnham-Fay

Ellis

2017

Precision Engineering

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Displacement measuring interferometry has high resolution and high dynamic range, which is widely used in displacement metrology and sensor calibration. Due to beam leakage in the interferometer, imperfect polarization components, and ghost reflections, the displacement measurement suffers from periodic error, whose pitch is multiple harmonics of the Doppler frequency. In dynamic measurements, periodic error is usually on the order of nanometers, which impacts the dynamic measurement accuracy. This paper presents an approach to estimate and correct periodic error in real time based on an extended Kalman filter, which has the capability to deal with both constant and non-constant velocity motions. This algorithm is implemented on an application-specific hardware architecture in an FPGA, which has advantages in throughput and resource usage compared with conventional implementations. The measurement validation shows that this approach can effectively eliminate the periodic error for both constant and non-constant velocity motion, and the residual error reaches to the level of the background noise of the interferometer.

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“…Therefore, we use a compensation method [10], which can reduce nonlinearity error of a homodyne interferometer in a real-time manner. By applying the real-time compensation method, the thickness can be measured with higher accuracy without a post processing, and an in-line inspection system can be constructed, of which measurement speed is not limited by the calculation process.…”

Section: Current Modulationmentioning

confidence: 99%

“…However, this method may be more sensitive to signal noise compared with the fitting method, since the parameter values are calculated using only several data values. This disadvantage can be reduced by increasing a tolerance determining coincidence of the current phase to the specific angles [10]. Figure 3 shows the schematic of the experimental setup for measuring thickness variation of glass panels.…”

Section: Current Modulationmentioning

confidence: 99%

Quadrature laser interferometer for in-line thickness measurement of glass panels using a current modulation technique

et al. 2014

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A thickness measurement system is proposed for in-line inspection of thickness variation of flat glass panels. Multi-reflection on the surfaces of glass panel generates an interference signal whose phase is proportional to the thickness of the glass panel. For accurate and stable calculation of the phase value, we obtain quadrature interference signals using a current modulation technique. The proposed system can measure a thickness profile with high speed and nanometric resolution, and obtain higher accuracy through real-time nonlinear error compensation. The thickness profile, measured by a transmissive-type experimental setup, coincided with a comparative result obtained using a contact-type thickness measurement system within the range of ±40 nm. The standard deviations of the measured thickness profiles and their waviness components were less than 3 nm with a scanning speed of 300 mm/s.

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A digital signal processing module for real-time compensation of nonlinearity in a homodyne interferometer using a field-programmable gate array

Cited by 28 publications

References 7 publications

Linearization of the sensors characteristics: a review

Linearization of the sensors characteristics: a review

Real-time FPGA-based Kalman filter for constant and non-constant velocity periodic error correction

Quadrature laser interferometer for in-line thickness measurement of glass panels using a current modulation technique

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