Application of Wavelet Digital Filter of Fourier Transform Profilometry in 3-D Measurement

2004 ◽  
Vol 471-472 ◽  
pp. 654-657
Author(s):  
Yun Shan Wang ◽  
S. Fu ◽  
Jin Quan Xu ◽  
Can Lin Zhou ◽  
S.C. Si ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Wavelet Transform ◽  
Digital Filter ◽  
High Frequency ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Fourier Transform Profilometry ◽  
Low Pass ◽  
Phase Demodulation

Fourier transform profilometry in 3-D measurement based on wavelet digital filter is presented in this paper. Before phase demodulation, original modulated grating image is handled with wavelet transform in order to remove the background components and high frequency. This method resolves spectrum overlapping at some extent and reduces the requirement of low-pass filter.

Rapid Recovery of Wide-Bandwidth Photothermal Signals via Homodyne Photothermal Spectrometry: Theory and Methodology

1993 ◽  
Vol 47 (4) ◽  
pp. 489-500 ◽  
Author(s):  
J. F. Power ◽  
M. C. Prystay
Keyword(s):  
High Frequency ◽  
Low Cost ◽  
Signal Recovery ◽  
Wide Bandwidth ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Filter Output ◽  
Low Pass ◽  
Four Quadrant ◽  
Lock In

Homodyne photothermal spectrometry (HPS) is a very wide bandwidth signal recovery technique which uses many of the elements of lock-in detection at very low cost. The method uses a frequency sweep, with a high-frequency bandwidth of up to 10 MHz, to excite a linear photothermal system. The response sweep of the photothermal system is downshifted into a bandwidth of a few kilohertz by means of in-phase mixing with the excitation sweep with the use of a four-quadrant double-balanced mixer and a low-pass filter. Under conditions derived from theory, the filter output gives a good approximation to the real part of the photothermal system's frequency response, dispersed as a function of time. From a recording of this signal, the frequency and impulse response of the photothermal system are rapidly recovered at very high resolution. The method has been tested with the use of laser photopyroelectric effect spectrometry and provides an inexpensive, convenient method for the recovery of high-frequency photothermal signals.

Treatment of Noise in Experimental Transport Measurements Plots With Discrete Wavelet Transforms

2009 ◽  
Author(s):  
Rube´n Panta Pazos
Keyword(s):  
Wavelet Transform ◽  
Wavelet Transforms ◽  
Transport Theory ◽  
Discrete Wavelet ◽  
Transform Method ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Low Pass ◽  
Thresholding Algorithm ◽  
High Pass

In this work it is applied the wavelet transform method [2] in order to reduce diverse type of noises of experimental measurement plots in transport theory. First, suppose that a problem is governed by the transport equation for neutral particles, and an unknown perturbation occurs. In this case, the perturbation can be associated to the source, or even to the flux inside the domain X. How is the behavior of the perturbed flux in relation to the flux without the perturbation? For that, we employ the wavelet transform method in order to compress the angular flux considered as a 1D, or n-th dimensional signal ψ. The compression of this signal can be performed up to some a convenient order (that depends of the length of the signal). Now, the transport signal is decomposed as [9, 11]: ψ=〈am|dm|dm−1|dm−2|⋯|d2|d1〉 where ak represents the sub signal of k-th level generated by the low-pass filter associated to the discrete wavelet transform (DWT) chosen, and dk the sub signal of k-th level generated by the high-pass filter associated to the same DWT. It is applied basically the Haar, Daub4 and Coiflet wavelets transforms. Indeed, the sub signal am cumulates the energy, for this work of order 96% of the original signal ψ. A thresholding algorithm provides treatment for the noise, with significant reduction in the compressed signal. Then, it is established a comparison with a base of data in order to identify the perturbed signal. After the identification, it is recomposed the signal applying the inverse DWT. Many assumptions can be established: the rate signal-to-noise is properly high, the base of data must contain so many perturbed signals all with the same level of compression. The problem considered is for perturbations in the signal. For measurements the problem is similar, but in this case the unknown perturbations are generated by the apparatus of measurements, problems in experimental techniques, or simply by random noises. With the same above assumptions, the DWT is applied. For the identification, it is used a method evolving statistical and metric techniques. It is given some results obtained with an algebraic computer system.

Vibrational Fatigue Analysis of a Strain Loading Using the Frequency and Wavelet Filtering Methods

2011 ◽  
Vol 462-463 ◽  
pp. 124-129
Author(s):  
Shahrum Abdullah ◽  
Edisah Putra Teuku ◽  
Zaki Nuawi Mohd. ◽  
Mohd. Nopiah Zulkifli
Keyword(s):  
High Frequency ◽  
Filter Design ◽  
High Amplitude ◽  
Morlet Wavelet ◽  
Wavelet Filtering ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Automotive Components ◽  
Low Pass ◽  
Low Amplitude

This paper presents a comparison work between the filtering methods of fatigue strain loadings using the frequency spectrum and the wavelet transform (WT), in which a raw loading signal can be simplified for purpose of simulation. For this reason, the Fast Fourier Transform (FFT) and the Morlet wavelet algorithms were used in order to transform the vibrational fatigue time series into the frequency domain signal, leading to the observation of the frequency characteristics of the signal. To retain high amplitude cycles in the FFT algorithm, a low pass filter technique was applied to remove the high frequency signals with small amplitude that are non-damaging. The departure of high frequency information smoothed the low amplitude cycles at high frequency events in the fatigue signal. The Butterworth filter was selected as the most efficient filter design as it retained most of the fatigue damage and also had the capability to remove 30 % of the original low amplitude cycles. On the other hand, the Morlet wavelet managed to remove 64 % of the original 59 second signal. This wavelet filtering method removed 34 % more than the similar procedure applied through the FFT approach. Hence, this fatigue data summarising algorithm can be used for studying the durability characteristics of automotive components.

Closed horizontal wire loop as a low–pass filter in tem measuring systems

2020 ◽  
Author(s):  
Nikolay O. Kozhevnikov ◽  
Keyword(s):  
Frequency Response ◽  
High Frequency ◽  
External Noise ◽  
Measuring System ◽  
Electromagnetic Noise ◽  
Measuring Systems ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Low Pass ◽  
Horizontal Wire

The paper discusses the possibility of using a closed horizontal loop in a TEM measuring system to reduce the external high–frequency electromagnetic noise induced in a receiving loop. It is shown that the effect of an additional loop on the frequency response of the TEM measuring system is similar to that of a low–pass filter. In order to effectively reduce external noise, one should locate the auxiliary loop as close as possible to the receiver one.

Design of the Broadband Standard Signal Generator for Laser Locating System of the Mine Hoisting Container

2013 ◽  
Vol 427-429 ◽  
pp. 2033-2036
Author(s):  
Di Fan ◽  
Yan Gao ◽  
Yue Zhao
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Frequency Standard ◽  
Analog Filters ◽  
Laser Ranging ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Noise Disturbance ◽  
Standard Signal ◽  
Low Pass

As the key junction between the ground and underground, hoisting systems as well as mines themselves are of vital importance to coalmine production. Laser ranging method is studied as a new solution of getting the real-time position directly. Furthermore, multi-scale phase based laser ranging principles are utilized in the system. The paper is aimed to conduct research into the problems existing in standard signal generating while using laser to locating the hoisting container, and to design standard sine generator circuits with DDS technology and DDS devices AD9850 to generate multiple frequency standard signals. In view of the serious noise disturbance in high frequency output, 4-order Chebyshev low-pass filter is designed, by using the integrated analog filters LT 6600-15, to filter the sine signals from AD9850 and to effectively weaken the noise disturbance. The established practical circuits are tested, obtaining trillion level high frequency and low frequency sine signals and fulfilling the requirements for the location system of hoisting containers.

A modified Bessel filter for amplitude demodulation of respiratory electromyograms

1998 ◽  
Vol 84 (1) ◽  
pp. 378-388 ◽  
Author(s):  
Ronald S. Platt ◽  
Eric A. Hajduk ◽  
Manuel Hulliger ◽  
Paul A. Easton
Keyword(s):  
High Frequency ◽  
Stop Band ◽  
Pass Band ◽  
Third Order ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Transient Characteristics ◽  
Low Pass ◽  
Seventh Order ◽  
Frequency Components

Platt, Ronald S., Eric A. Hajduk, Manuel Hulliger, and Paul A. Easton. A modified Bessel filter for amplitude demodulation of respiratory electromyograms. J. Appl. Physiol. 84(1): 378–388, 1998.—We studied a device that is commonly used for amplitude demodulation of respiratory muscle electromyograms (EMG). This device contains a rectifier and a low-pass filter called a modified third-order Paynter filter. We characterized this filter and found that it has good transient characteristics that suit its task as an EMG demodulator, but it has poor high-frequency attenuation that passes interfering, higher frequency components to the output waveform. Therefore, we designed and constructed a new filter with transient characteristics that are comparable to those of the modified Paynter filter but with superior high-frequency attenuation. This new filter is a modified seventh-order Bessel filter. We also identified a simple technique to convert an existing modified Paynter filter back to an original Paynter filter. The original Paynter filter has a wider pass band than the modified Paynter filter but superior stop-band attenuation.

Suprathreshold Intrinsic Dynamics of the Human Visual System

2003 ◽  
Vol 15 (12) ◽  
pp. 2883-2908 ◽  
Author(s):  
Gopathy Purushothaman ◽  
Haluk Öğmen ◽  
Harold E. Bedell
Keyword(s):  
Visual System ◽  
Human Visual System ◽  
High Frequency ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Cortical Dynamics ◽  
Neural Activities ◽  
Low Pass ◽  
Psychophysical Studies ◽  
Spatiotemporal Integration

Intrinsic high-frequency neural activities have been observed in the visual system of several species, but their functional significance for visual perception remains a fundamental puzzle in cognitive neuroscience. Spatiotemporal integration in the human visual system acts as a low-pass filter and makes the psychophysical observation of high-frequency activities very difficult. A computational model of retino-cortical dynamics (RECOD) is used to derive experimental paradigms that allow psychophysical studies of high-frequency neural activities. A reduced-parameter version of the model is used to quantitatively relate psychophysical data collected in two of these experimental paradigms. Statistical analysis shows that the model's account of the variance in the data is, in general, highly significant. We suggest that psychophysically measured oscillations reflect intrinsic neuronal oscillations observed in the visual cortex.

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