Biomedical subjects

Huai Min Shang

Publications and source records attributed to Huai Min Shang.

4 recordsLinked to original sources

PubMed2003

Height measurement of microchip connecting pins by use of stereovision.

A stereovision method for estimating the height of connecting pins on a microchip is described. The technique uses a centroidal method to simplify the calculation. A few seconds are required for a Pentium 586 PC to calculate the heights of 300 connecting pins on a 50 mm x 50 mm microchip. The method is described, and experimental results are presented. The optical system, which consists of two CCD cameras with long-focal-length lenses and a two-channel digital image grabber, is capable of in situ measurement.

Journal Article↗

PubMed2003

Shape measurement by use of liquid-crystal display fringe projection with two-step phase shifting.

The use of an optical fringe projection method with two-step phase shifting for three-dimensional (3-D) shape measurement of small objects is described. In this method, sinusoidal linear fringes are projected onto an object's surface by a programmable liquid-crystal display (LCD) projector and a long-working-distance microscope (LWDM). The image of the fringe pattern is captured by another LWDM and a CCD camera and processed by a phase-shifting technique. Usually a minimum of three phase-shifted fringe patterns is necessary for extraction of the object shape. In this method, a new algorithm based on a two-step phase-shifting technique produces the 3-D object shape. Unlike in the conventional method, phase unwrapping is performed directly by use of an arccosine function without the need for a wrapped phase map. Hence, shape measurement can be speeded up greatly with this approach. A small coin is evaluated to demonstrate the validity of the proposed measurement method, and the experimental results are compared with those of the four-step phase-shifting method and the conventional mechanical stylus method.

Journal Article↗

PubMed2002

Proposed algorithm for phase unwrapping.

A new, to our knowledge, two-dimensional phase-unwrapping algorithm is proposed. The algorithm, which is based on the global continuity of physical information (e.g. the three-dimensional surface profile of an object) being measured, uses the principle of least-phase difference to rectify errors caused by an erroneous 2pi-phase jump in the initial unwrapped phase map obtained by the conventional phase-unwrapping method. Experimental results show that the proposed algorithm works well on a phase map that contains error sources, such as noises, phase discontinuity of more than pi, and insufficient sampling. Moreover, the algorithm is most suitable for unwrapping a phase map generated during shape measurement with a step-change surface on the test object, which is usually a critical problem in shape measurement.

Journal Article↗

PubMed2002

Investigation of membrane deformation by a fringe projection method.

An optical method has been developed to measure the deformation of a membrane in a microphone. A fringe projector that consists of an optical fiber and an optical wedge is described and analyzed by geometric optics. A three-step phase-shifting technique that involves the introduction of an arbitrary phase is discussed. The fine fringe patterns projected onto a small test surface are captured by a CCD camera mounted on a long-distance microscope. With the aid of a phase-shifting technique and signal-demodulating techniques, the proposed setup is capable of measuring deformation of the membrane of the order of as much as submicrometers.

Journal Article↗