Biomedical subjects

Wanli Chi

Publications and source records attributed to Wanli Chi.

2 recordsLinked to original sources

PubMed2006

Light-emitting diode illumination design with a condensing sphere.

An illumination system is described that comprises a glass or plastic sphere, an embedded light-emitting diode (LED) source, and a reflecting or scattering mirror. The rays from the LED are either refracted in the forward direction or totally internally reflected by the sphere. The mirror breaks the total internal reflection and thus sends the rays in the forward direction. The illumination pattern and efficiency of the system are analyzed. This system is extremely compact and efficient and is a good starting point for a complex illumination system design.

Journal Article↗

PubMed2003

Computational imaging with the logarithmic asphere: theory.

A theory for an integrated system is described that combines a logarithmic aspheric imaging lens with maximum-entropy digital processing to extend the depth of field ten times over that of a conventional lens and to provide near-diffraction-limited resolution. Two types of logarithmic aspheres are derived that are circularly symmetric lenses with controlled continuous radial variation of focal length. The details of an iterative maximum-entropy algorithm are also presented. The properties of convergence and speed of the algorithm are greatly improved by introducing a metric parameter to adjust the weight of different pixel values of the recovered picture in each loop properly.

Journal Article↗