Many textures such as woven fabrics and composites have a regular and repeating texture. This paper presents a new method to capture the texture information using adaptive wavelet bases. Wavelets are compact functions which can be used to generate a multiresolution analysis. Texture constraints are used to adapt the wavelets to better characterize specific textures. An adapted wavelet basis has very high sensitivity to the abrupt changes in the texture structure caused by defects. This paper demonstrates how adaptive wavelet basis can be used to locate defects in woven fabrics. © 1996 Society of Photo-Optical Instrumentation Engineers.

Images of a woven fabric with missing picks are digitized, and three different image analysis techniques are compared: the Sobel edge operator, the fast Fourier transform, and the discrete wavelet transform. The wavelet transform, used as a multi-resolution spectral filter, is able to give both spectral and frequency information about a fabric. For the samples tested, the wavelet transform can characterize defects due to missing picks and ends faster and more accurately than the other methods.

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Solvent-induced performance deterioration in corona charged polypropylene electret filter media was studied. Electret media, exposed to isopropanol (IPA) in the liquid phase, exhibited reduced filtration efficiency with negligible changes in the pressure drop across the media. Scanning electron microscopy imaging indicated no observable morphological changes after IPA exposure. Solvent-induced efficiency deterioration of electret filter media was hypothesized to originate from charge deterioration rather than charge masking. The charge of the individual fibers in filter media was characterized using electrostatic force microscopy (EFM). EFM investigation produced evidence that exposure to IPA in the liquid phase affected the electrostatic charges on fibers. Exposure to organic solvents such as xylene, toluene, and ethyl benzene has been reported to increase charge mobility in polypropylene fibers, thereby reducing the electrostatic charge and the ability of the fibers in the electret filter media to capture particulates.

Summary Electrostatic force microscopy was used to directly probe solvent‐induced charge degradation in electret filter media. Electrostatic force gradient images of individual polypropylene electret fibres were used to quantify the extent of charge degradation caused by the immersion of the fibres into isopropanol. Electrostatic force gradient images were obtained by monitoring the shifts in phase and frequency between the oscillations of the biased atomic force microscopy (AFM) cantilever and those of the piezoelectric driver. Electrostatic force microscopy measurements were performed using non‐contact scans at a constant tip‐sample separation of 75 nm with varied bias voltages applied to the cantilever. Mathematical expressions, based on the capacitance of the tip‐sample system, were used to model the phase and frequency shifts as functions of the applied bias voltage to the tip and the offset voltage due to the fibre's charge. Quantitative agreement between the experimental data and the simplified model was observed.

To act as an alternative to existing systems, image-based fiber length measurements must yield precise results in a reasonable amount of processing time. To be used as a calibration device for current systems, the processing time becomes less important than accuracy and precision. Here, we report on the accuracy and precision of image processing applications compared with existing methods of HVI, AFIS, and hand measurements. Further, we propose preferred system parameters for these two possible applications of the technology.

The charge of a corona charged electret fiber as well as an uncharged glass fiber was characterized via Electrostatic Force Microscopy (EFM). Electrostatic force gradient images were obtained by monitoring the shifts in phase between the oscillations of the biased EFM cantilever and those of a piezoelectric driver. EFM measurements were performed using noncontact scans at a constant tip-sample separation of 75 nm with varied bias voltages applied to the cantilever. A mathematical expression, based on the Coulombic and induced polarization effects, were used to model the EFM phase shifts as a function of the applied tip bias voltages. There was quantitative agreement between the experimental data and the mathematical expression, and the quantitative interpretation for charges on the fiber was made.