A fundamental limitation to the use of single-point absorbance detection for capillary electrophoresis is irradiance, since it is not possible to create an image at the detection point on capillary that is brighter than the light source. This limitation may be overcome by illuminating a length of the capillary using a fiber-optic bundle and using a charge coupled device (CCD) camera that can image the full length of the illuminated zone. The present paper describes design and development of a CCD detector for UV absorbance that can be used in both multiwavelength and single-wavelength modes. The CCD camera images analyte peaks in the capillary dimension, together with wavelength-resolved absorbance in the dimension perpendicular to the capillary. Successive snapshots of the peaks are added together, after appropriate correction for time-dependent peak displacement, without sacrificing spatial resolution. Measured baseline rms noise values at 200 nm are 34 μAU using a holographic grating in multiwavelength mode and 8 μAU with the addition of a band-pass filter. Both values are in excellent agreement with calculations of limiting shot noise. Performance in multiwavelength mode is constrained by the 470-ms readout time of the CCD used, which sets a maximum duty cycle of 2.3%. Noise contributions from source intensity fluctuations are reduced by using a portion of the CCD image to provide a baseline reference signal. With 4-hydroxybenzoate as test analyte, the linear dynamic range in multiwavelength mode is shown to be between 3 and 4 orders of magnitude. High-quality spectra of 2-, 3-, and 4-methylbenzoates are obtained on capillary and used in deconvolution of closely migrating peaks of the 2- and 3-isomers.
The paper describes work relating to the laser line triangulation technique which has been used to inspect the edges of overlapping shoe components prior to the sewing operation. The laser line triangulation technique involves projecting a laser line on to a surface which can be viewed using an area camera. A surface height transition (edge) causes a discontinuity in the observed laser line. Different approaches for extracting the edge positions in the image co‐ordinate system have been investigated based on the Hough transform, the spatial histogram, polynomial regression and the discrete first derivative. These edge detection algorithms are compared in terms of speed and precision performance. Three‐dimensional scans of typical shoe component parts are presented.
This paper presents a novel approach for intensity calculation of X-ray diffraction spots based on a two-stage radial basis function (RBF) network. The ®rst stage uses pre-determined reference pro®les from a database as basis functions in order to locate the diffraction spots and identify any overlapping regions. The second-stage RBF network employs narrow basis functions capable of local modi®cations of the reference pro®les leading to a more accurate observed diffraction spot approximation and therefore accurate determination of spot positions and integrated intensities.
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