Traditional Optical Method Research Articles

Self-calibrating measurement of high-speed electro-optic phase modulators based on two-tone modulation.

We propose a self-calibrating method for high-frequency response measurement of electro-optic phase modulators based on two-tone modulation. The method utilizes the electrical domain measurement of heterodyning spectrum between the two-tone modulation optical signal and the frequency-shifted optical carrier, and eliminates the need to correct the responsivity fluctuation in the photodetection. High-frequency modulation depth and half-wave voltages are measured and compared to those with the traditional optical spectrum analysis method in the experimental demonstration. The proposed method enables calibration-free and accurate frequency response measurement of electro-optic phase modulators by using high-resolution electrical spectrum analysis.

Dynamic Targets Detection for Robotic Applications Using Panoramic Camera Based on Optical Flow

Optical flow method is an important and valid method in the field of detection and tracking of moving objects for robot inspection system. Due to the traditional Horn-Schunck optical flow method and Lucas-Kanade optical flow method cannot meet the demands of real-time and accuracy simultaneously, an improved optical flow method based on Gaussian image pyramid is proposed. The layered structure of the images can be obtained by desampling of the original sequential images so that the motion with the high speed can be changed into continuous motion with lower speed. Then the optical flows of corner points of the lowest layer will be calculated by the LK method and be delivered to the upper layer and so on. Thus the estimated optical flow vectors of the original sequential images will be obtained. In this way, the requirement of accuracy and real time could be met for robotic moving obstacle recognition.

Measurement of large convex hyperbolic mirrors using hindle and stitching methods

Based on the traditional Hindle-Sphere method and Subaperture stitching method, we introduce a measurement method for large convex hyperbolic mirrors. This method uses a small sphere to get the subaperture's surface shape of the convex hyperbolic mirror, and then uses the stitching method to get the full-aperture surface shape. The experimental demonstrations were performed on a convex hyperbolic mirror with our method. The results show that the repeatability of the RMS is 0.002λ (3σ). Compared with the traditional optical compensation method, it is shown that our results are in good agreement with it. Our method can get high-precision full-aperture surface shapes; furthermore, the cost of maintaining it is relatively low and the operation is convenient.

Direct measurement of macro contact angles through atomic force microscopy

The information of liquid film profile near a three-phase contact line is critical for a comprehensive understanding of various wetting and phase-change phenomena. Despite numerous theoretical and simulation studies, an accurate measurement on the thin film profile is difficult due to its very small scale. In the present work, a state-of-the-art atomic force microscopy (AFM) under tapping mode (TM) was employed to achieve a high-power scanning across the contact line. Within a scale of several to tens of microns, a highly linear film profile is observed near the contact line, based on which the contact angle is extracted. Comparing to the macro contact angle measured by the traditional optical method, the AFM result shows good agreement but achieves much higher precision. Moreover, the sub-micron thin film that is beyond the capability of the optical method was observed, in which the film profile is not linear and the concept of macro contact angle is not valid.

Comparison of an electrochemical biosensor with optical devices for hemoglobin measurement in human whole blood samples

BackgroundAn electrochemical based biosensor for hemoglobin measurement was developed as an alternative to the traditional optical method, and underwent testing for use in professional settings. MethodsThe affects of samples' freshness, hemolysis, bilirubin on the electrochemical method, as well as the repeatability, precision and accuracy were studied, using optical method devices as references. ResultsSamples were stored at room temperature or in a cold environment for 7days, partially or completely hemolyzed samples, and samples containing bilirubin with a concentration of up to 150mg/l were investigated with no effects for interfering studies. Repeatability of finger blood testings was verified with six consecutive tests on nine volunteers, results ranged from 3% to 8% variation. The test results of BeneCheck were correlated with Sysmex, Beckman Coulters, Cell-Dyn and HemoCue methods, the results have shown similar and 95% of test results were within a ±15% bias. ConclusionsBeneCheck hemoglobin test system performed well and accurately, while requiring 1μl of blood sample and 10s detection time. Based on the cost, accuracy, sample volume, measuring time, ease of viewing and portability, BeneCheck deliver the best characteristics for these purposes.

Nano-optical information storage induced by the nonlinear saturable absorption effect

Nano-optical information storage is very important in meeting information technology requirements. However, obtaining nanometric optical information recording marks by the traditional optical method is difficult due to diffraction limit restrictions. In the current work, the nonlinear saturable absorption effect is used to generate a subwavelength optical spot and to induce nano-optical information recording and readout. Experimental results indicate that information marks below 100 nm are successfully recorded and read out by a high-density digital versatile disk dynamic testing system with a laser wavelength of 405 nm and a numerical aperture of 0.65. The minimum marks of 60 nm are realized, which is only about 1/12 of the diffraction-limited theoretical focusing spot. This physical scheme is very useful in promoting the development of optical information storage in the nanoscale field.

Human abnormal behavior identification algorithm based on time-spatial Markov random field

Concerning the sudden-violence abnormal behavior between people an algorithm which could identify abnormal behavior and other normal behaviors more accurately from images was proposed.This algorithm was based on traditional image segmentation technique adopted the feature of neighborhood-related-only and the motion feature of adjacent frame in Markov Random Field MRF reconstructed the Gibbs energy function.This algorithm considered not only the spatial-information between every pixel and its neighborhood but also the time-information between successive frames was added in to calculate the whole energy value in the acquired images which those energy data could be analyzed by using the energy curve.Finally the effectiveness of this approach has been proved by comparing with the traditional optical flow method.

Critical assessment of DTA–DSC methods for the study of nucleation kinetics in glasses

Microscopy methods are usually employed to estimate the number density of super critical nuclei and the resulting crystal nucleation rates, I( T). These traditional techniques rely on a double-stage treatment, i.e. the development of the nuclei at a temperature higher than the previous nucleation temperature up to a size large enough to be visible with optical or electron microscopy. These methods can give reliable results for I( T), but are rather laborious and time-consuming. On the other hand, non-isothermal (DTA/DSC) methods are, in principle, much faster. In this paper, we experimentally test two non-isothermal methods by comparison with a traditional optical microscopy method. We found that, if they are properly employed, non-isothermal methods can give useful kinetic information, which includes the crystal number density and nucleation rates, but to get accurate quantitative data they need some preliminary information about nucleation and growth rates in the studied glass and, in addition, are as laborious as the traditional microscopy methods!

Double tungsten coil atomic emission spectrometry: signal enhancement and a new gas phase temperature probe

A new double atomizer arrangement for tungsten coil atomic emission spectrometry is described. Two small constant current power supplies, a Czerny–Turner spectrograph, and a charge coupled device (CCD) detector are used to determine refractory elements in water samples. The analytical figures of merit for Ba, Sr, Ti, and V are reported and compared with the single coil arrangement. The use of two atomizers provides more energy for the atomization and excitation of the analytes and consequently improves sensitivity. Addition of a second coil improves limits of detection for refractory elements by a factor of 40 (V) and 5 (Ti). Using 25 µl sample volumes, the limit of detection for V is 10 µg l−1 at the 437.9 nm emission line, and 400 µg l−1 for the 399.9 nm Ti emission line. Vanadium is determined in a polluted water certified reference material, and the results agree with the certified value (250 mg l−1) at the 95% confidence level. For Ba and Sr, which emit strongly with a single coil, the double coil detection limits are improved by less than a factor of two: 0.007 µg l−1Ba and 0.4 µg l−1Sr. Emission signals for Ag, Cu and Sn are observed for the fist time with a tungsten coil atomic emission spectrometry (WCAES) system. A new method to determine the gas phase temperature by atomic emission spectrometry is also presented. Emission intensities for Dy (418.7 and 421.1 nm) and Eu (462.7 and 466.2 nm) are used to calculate Boltzmann temperatures for both the single and double coil arrangements. Temperature values calculated by this method agree with the traditional optical two-line absorption method using Sn (284.0 and 286.3 nm).

Point matching under large image deformations and illumination changes

To solve the general point correspondence problem in which the underlying transformation between image patches is represented by a homography, a solution based on extensive use of first order differential techniques is proposed. We integrate in a single robust M-estimation framework the traditional optical flow method and matching of local color distributions. These distributions are computed with spatially oriented kernels in the 5D joint spatial/color space. The estimation process is initiated at the third level of a Gaussian pyramid, uses only local information, and the illumination changes between the two images are also taken into account. Subpixel matching accuracy is achieved under large projective distortions significantly exceeding the performance of any of the two components alone. As an application, the correspondence algorithm is employed in oriented tracking of objects.

Detection ofsalmonella typhimurium by hand-held ion mobility spectrometer: A quantitative assessment of response characteristics

Salmonella typhimurium was determined with the use of a combination of an enzyme-linked inmmunosorbent assay (ELISA), a phosphatase mediated end step, and a hand-held ion mobility spectrometer for detecting phenol, the ELISA reaction product. Elevated temperature and low solution pH improved the efficiency for thermal desorption of phenol from filter paper strips; still, the thermal desorption profile was broad and occurred over a 2–3.5-min range. As a result, the detection limits were restricted to ∼104 bacteria in 10-μl aliquots of sample. Precision of quantitative response with a hand-held ion mobility spectrometry (IMS) analyzer ranged from 0.7%–42% relative standard deviation (RSD) for 0–10 μg of phenol, and the precision mean was 12% RSD. Thermal and hydrolytic stability of phenylphosphate, the substrate for ELISA reactions, was excellent in buffer solution, without detectable degradation for over 60 days at temperatures from −70 to 45 °C. Response to increasing levels of S. typhimurium antigen by IMS correlated with a traditional optical spectrophotometric method and showed comparable detection limits. Calculations portend a 100-fold improvement in detection limits through only improved engineering of an ELISA-IMS interface. © 1997 John Wiley & Sons, Inc.

Surface tension by pendant drop: I. A fast standard instrument using computer image analysis

An improved method has been developed for the determination of surface and interfacial tensions from primary drop shape data. In addition, wetting angles of sessile drops may be determined. The method has been built around a commercial pendant drop instrument and an IBM-compatible PC with a frame grabber card. In order to differentiate the drop profile, a filter routine using a local threshold and interpolation technique has been developed that is combined with an edge-tracing algorithm. The program for calculation of surface tension is divided into two parts. The first part is based on the traditional optical method and uses inflection of the drop profile. By means of several polynomial interpolations and curve fitting of theoretical profiles, the form factor β and surface tension γ are determined. The second part of the calculation utilizes the above values as a first estimate and then performs a further optimalization of γ by comparison between experimental and theoretical Young—Laplace profiles. With a PC AT with a 80287 mathematical coprocessor the measurements take about 5 s and the reproducibility is typically 0.01–0.03 mN/m for a wide range of known liquids.