No abstract

We have demonstrated high color rendering index (CRI) and chromatic stability of top‐emitting white organic light‐emitting diodes (TEWOLEDs) by capping a supplementary green color conversion layer (CCL) on the cathode of single blue emitter based TEWOLEDs. By employing CCLs, blue photon energy is absorbed and converted to green emission efficiently, resulting in an improvement of CRI from 72 to 86. We attribute the increased high CRI to the broadening of the out‐coupled spectrum and an appropriate intensity match among the three primary colors. Meanwhile, the TEWOLEDs show extremely high chromatic stability. The results indicate that this method provides a new avenue to improve the CRI of TEWOLEDs. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

We have fabricated multi‐peak and chromaticity‐stable top‐emitting white organic light‐emitting diodes (TEWOLEDs) using single blue emitter. Besides the intrinsic emission of blue emitter, the additional emission can be well realized by simply adjusting the thickness of hole transporting layer (HTL), thus modifying the optical cavity length to obtain different resonant wavelengths. The detailed variation process for multi‐peak spectra with the increase of HTL thickness is studied, which provides a guidance for the design of microcavity TEWOLEDs. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Methods of position tracking based on magnetic field monitoring have been widely studied. The application of electromagnetic tracking (EMT) in endoscopic procedures not only has high requirements for position accuracy but also has a great demand for orientation accuracy. Accurate orientation information can provide more clues for shape fitting of the endoscope, especially when coils are placed at the front end of the endoscope for front end shape reconstruction. However, few methods have been proposed to calibrate position and orientation errors at the same time, while most methods are focused on position error correction. This paper presents a new method showing that by separating the tracking space into grids and calibrating the grid-sensing coil position and orientation parameters (GSCPOP), the position and orientation accuracy can be improved simultaneously by means of iterative computation. Compared to the uncalibrated method, position accuracy showed a 285% improvement, and orientation accuracy showed a 129% improvement.

Determining the shape and position of endoscopes has considerable benefits in endoscopic diagnosis and treatment. However, electromagnetic field distortion caused by metal materials, limited field strength and multiple sensors complicate the endoscope localization problem. In this paper, a locally weighted method for the electromagnetic localization of endoscopes that combines the models of the location problem and the errors is proposed. A hardware system, test platform and fixtures are constructed to collect data and evaluate the method. To obtain the global minimum of the objective function, an approach that combines a genetic algorithm with the Levenberg-Marquardt algorithm is developed. Compared to the localization method without weighting, the results show a 5.3:1 improvement in the localization of a naked coil and a 2.4:1 improvement in the localization of a coil inside a piece of endoscope insertion tube. In a transmitter-tracking configuration that limits the field strength and at a much farther distance (closer than 400 mm vs 400--700 mm), this method performs better than previously reported commercial systems in a similar environment. Furthermore, this method can greatly reduce the influence of metal materials used in endoscopes near the transmitter coil. This method can satisfy the demand for endoscope localization.