S.H. Wang

Bio: S.H. Wang is an academic researcher from National University of Singapore. The author has contributed to research in topics: Interferometry & Surface roughness. The author has an hindex of 14, co-authored 37 publications receiving 523 citations.

Development of a laser-scattering-based probe for on-line measurement of surface roughness

Abstract: The design and properties of an optical probe for on-line measurement of surface roughness are discussed. Based on light scattering, a probe that consists of a laser diode, a measuring lens, and a linear photodiode array was designed to detect surface roughness, in which the light scattered from a test surface at a relatively large scattering angle φ (=28°) can be collected to enhance measuring range and repeatability. A coaxial design that incorporates a dual-laser probe and compressed air makes the proposed system insensitive to the position of the test surface and to surface conditions such as the presence of debris, vibration, and lubricants that result from machining. The results from measurements of several sets of specimens have demonstrated the feasibility of measuring surface roughness by using light scattering. On-line measurement on a diamond-turning lathe has shown that the proposed technique is stable and compact enough to be applicable to on-line measurement of surface roughness of an engineering surface.

Surface roughness measurement in the submicrometer range using laser scattering

Abstract: A technique for measuring surface roughness in the submi- crometer range is developed. The principle of the method is based on laser scattering from a rough surface. A telecentric optical setup that uses a laser diode as a light source is used to record the light field scattered from the surface of a rough object. The light intensity distribu- tion of the scattered band, which is correlated to the surface roughness, is recorded by a linear photodiode array and analyzed using a single- chip microcomputer. Several sets of test surfaces prepared by different machining processes are measured and a method for the evaluation of surface roughness is proposed. © 2000 Society of Photo-Optical Instrumentation Engineers. (S0091-3286(00)00406-2)

Laser integrated measurement of surface roughness and micro-displacement

Abstract: An optical method based on laser scattering and optical triangulation for measurement of surface roughness and micro-displacement measurement is proposed. The technique allows evaluation of surface roughness and micro-displacement of a specimen using just one device. The principle of the method and the basic instrumentation design are described and the validity of the principle is demonstrated by experimental evaluations. Results show that, for specimens with surface roughnesses (Ra ) in the range 0.005 - 0.1 µm, displacements in the range ±300 µm can be readily measured.

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

Abstract: A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.

State-of-The-Art and Applications of 3D Imaging Sensors in Industry, Cultural Heritage, Medicine, and Criminal Investigation

Abstract: 3D imaging sensors for the acquisition of three dimensional (3D) shapes have created, in recent years, a considerable degree of interest for a number of applications. The miniaturization and integration of the optical and electronic components used to build them have played a crucial role in the achievement of compactness, robustness and flexibility of the sensors. Today, several 3D sensors are available on the market, even in combination with other sensors in a “sensor fusion” approach. An importance equal to that of physical miniaturization has the portability of the measurements, via suitable interfaces, into software environments designed for their elaboration, e.g., CAD-CAM systems, virtual renders, and rapid prototyping tools. In this paper, following an overview of the state-of-art of 3D imaging sensors, a number of significant examples of their use are presented, with particular reference to industry, heritage, medicine, and criminal investigation applications.

Optical sensors

Abstract: Optical sensor development has been pursued over past 25 years, which has also seen development of novel chemistries, materials, sensor designs and optical instrumentation. In addition, novel signal and data processing techniques have been adopted in the sensor development. New techniques and materials in chemical and biological sensing have set further stages of advanced research. One of the most recent technological advances in this area has been the development of optical nanosensors, which are sensors with dimensions on the nanometer scale. Nanosensors of various types (e.g. optical, electrochemical) have been published in the literature over the past decade. Optical nanosensors, like the larger and macro scale sensors, can be either chemical or biological, depending on the type of probe used. Both types of sensors have been studied to provide a reliable method of monitoring various chemicals in microscopic environments and have been used to detect molecules within single cells. The field of nanosensing is relatively new and reports in the literature presenting any problems associated with such a scale of analysis are sparse. This paper will briefly review some of the current developments in the field of optical nanosensors.

Hydrogel microparticles as dynamically tunable microlenses.

Abstract: Tunable micro-optical elements were prepared by aqueous free-radical polymerization and electrostatic self-assembly techniques. Stimuli-responsive poly(N-isopropylacrylamide-co-acrylic acid) (pNIPAm-AAc) microgels were used as lenses to generate dynamically tunable optical elements. By using optical microscopy to investigate the micrometer-scale dynamics of the self-assembled microlenses, we demonstrate focal length tuning through modulation of the solution pH and/or temperature.

Photogrammetric reconstruction of high-resolution surface topographies and deformable wing kinematics of tethered locusts and free-flying hoverflies

Abstract: Here, we present a suite of photogrammetric methods for reconstructing insect wing kinematics, to provide instantaneous topographic maps of the wing surface. We filmed tethered locusts (Schistocerc...