Development of the Heterodyne Laser Encoder System for the X–Y Positioning Stage

Chang, Cheng-Yuan; Tu, Tsung-Chun; Huang, Siang-Ruei; Wang, Yung-Cheng; Chang, Syuan-Cheng

doi:10.3390/s21175775

Cited by 3 publications

(5 citation statements)

References 20 publications

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“…Furthermore, in the multi-axis positioning task, the homodyne interferometer requires more optical elements and detectors to fit the differential signaling [ 19 ]. On the contrary, the heterodyne interferometer can share the reference signal, eliminating the need to arrange the reference signal for every positioning axis [ 6 ]. This characteristic is advantageous in the positioning application, especially for the multi-axis positioning systems [ 20 , 21 ].…”

Section: Methodsmentioning

confidence: 99%

“…The common heterodyne signal processing is based on LIA technology [ 22 , 23 ], and is wildly used in interferometer signaling [ 6 , 24 ]. The block diagram of the LIA method is shown in Figure 4 .…”

Section: Methodsmentioning

confidence: 99%

“…The common initial resolutions of the laser interferometers are about 0.32 μm or 0.16 μm, depending on the optical structure [ 2 ] ( Table S1, Supplementary Material ). The initial resolution of the laser interferometer is several times higher than that of a grating-based encoder system [ 3 ], and laser interferometers also have the feature of error reduction [ 4 , 5 , 6 ]. Therefore, the interferometry−based encoders have high potential in precision positioning.…”

Section: Introductionmentioning

confidence: 99%

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A Novel Analog Interpolation Method for Heterodyne Laser Interferometer

Chang

Wang

et al. 2023

Micromachines

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Laser interferometer technology is used in the precision positioning stage as an encoder. For better resolution, laser interferometers usually work with interpolation devices. According to the interpolation factor, these devices can convert an orthogonal sinusoidal signal into several square-wave signals via digital processing. The bandwidth of the processing will be the limitation of the moving speed of the positioning stage. Therefore, the user needs to make a trade-off between the interpolation factor and the moving speed. In this investigation, a novel analog interpolation method for a heterodyne laser interferometer has been proposed. This method is based on the principle of the lock-in amplifier (LIA). By using the proposed interpolation method, the bandwidth of the laser encoder system can be independent of the interpolation factor. This will be a significant benefit for the ultra-high resolution encoder system and the laser interferometers. The concept, design, and experiment are revealed in this manuscript. The experimental results show that the proposed interpolation method can reach nanometer resolution with a heterodyne laser interferometer, and the bandwidth of the signal is independent of the resolution.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A Novel Analog Interpolation Method for Heterodyne Laser Interferometer

Chang

Wang

et al. 2023

Micromachines

Self Cite

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“…Due to the significant advances in convolutional neural networks (CNNs) automating feature extraction through convolution on input data to derive high‐level features, as compared to the traditional manual feature extraction, CNNs automatically update convolution kernel parameters using the gradient descent algorithm to extract semantic information from input data, thereby reducing subjectivity in the model training process, [ 20 ] which have the potential to design an end‐to‐end gait assessment system. Currently, some research related to the abnormal gait analysis has shifted to CNNs.…”

Section: Introductionmentioning

confidence: 99%

Wearable Sensor‐Based Multi‐modal Fusion Network for Automated Gait Dysfunction Assessment in Children with Cerebral Palsy

Tang,

Wang,

Lian

et al. 2024

Advanced Intelligent Systems

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Gait, fundamental to human movement, becomes compromised in cerebral palsy (CP), a childhood‐onset central nervous system motor disorder. Precise assessment of patients’ gait is crucial for tailored rehabilitation interventions. Currently, clinical scales assessing CP gait dysfunction mostly, while valuable, rely on subjective clinician observations. To enhance objectivity and efficiency in CP diagnosis and rehabilitation, there is a need for more objective assessment procedures. This study introduces a multi‐modal and multi‐scale feature fusion (MMFF) framework, a new framework for automating gait dysfunction assessment in children with CP. By utilizing surface electromyography and acceleration signals recorded during children's walking, MMFF generates a feature vector enriched with adaptively refined feature maps, cross‐mode correlations, and both local and global information. Validation of MMFF's effectiveness is evident through an accomplished classification accuracy of 99.13%. The mean values for precision, recall, and F1‐score in Gross Motor Function Classification System (GMFCS)‐1, GMFCS‐2, and GMFCS‐3, reaching 99.00%, 99.00%, and 98.33%, respectively, further reflect the accuracy of functional assessments at each level. This study underscores MMFF's potential as an objective, streamlined tool for clinicians, promising improved gait assessment and well‐informed rehabilitation strategies for children with CP.

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“…To meet the process and performance requirements of chip manufacture, the measurement accuracy of the lithography machine’s displacement system must reach the subnanometer level [ 1 ]. At present, the measurement tools used in the field of ultraprecision displacement measurement mainly include heterodyne laser and grating interferometers [ 2 , 3 , 4 , 5 , 6 ].…”

Section: Introductionmentioning

confidence: 99%

Design and Implementation of a Subnanometer Heterodyne Interference Signal Processing Algorithm with a Dynamic Filter

Zeng

Zhao

Xiong

et al. 2022

Sensors

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In this study, a subnanometer heterodyne interference signal processing algorithm with a dynamic filter is proposed. The algorithm can effectively reduce the measurement error caused by the noise introduced in the optical path and circuit. Because of the low signal−to−noise ratio of the measurement signal, a dynamic filter with variable coefficients is designed. The role of the bi−quadrature lock−in amplifier algorithm in the problem of different amplitudes among the measurement signal, reference signal, and uncertainty of the frequency difference of the dual−frequency laser is analyzed. With the aid of the heterodyne interferometry platform, the error in the solution results of the proposed algorithm and the conventional algorithm is compared. The results indicate that the maximum deviation of the phase increment of the algorithm does not exceed 6 mrad, the single−cycle phase difference can be subdivided by 1024, and the system resolution reaches 0.15 nm.

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Development of the Heterodyne Laser Encoder System for the X–Y Positioning Stage

Cited by 3 publications

References 20 publications

A Novel Analog Interpolation Method for Heterodyne Laser Interferometer

A Novel Analog Interpolation Method for Heterodyne Laser Interferometer

Wearable Sensor‐Based Multi‐modal Fusion Network for Automated Gait Dysfunction Assessment in Children with Cerebral Palsy

Design and Implementation of a Subnanometer Heterodyne Interference Signal Processing Algorithm with a Dynamic Filter

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