In this letter, we present a new design for a light-emitting diode- based bike headlamp. The optical design contains two horizontal reflectors and a light pipe with two horizontal parallel mirrors. The designed illumination pattern in our simulations performs a contrast of 250 in the K-mark regulation, and it was measured to be 21 in the experiment with a not well-finished prototype, which was operated at 1 W. The contrast is higher than 5 as requested in the regulation.
In this work, an effective method for controlling light emission of light-emitting diodes(LEDs) is proposed to maintain
the light-emission characteristics. Wholly, there are two physical concepts of LEDs unutilized in this controlled method.
One concept is the forward voltage and the junction temperature of LEDs could be described as a simple and linear
relationship according to electric-thermal properties of LEDs. Thus the behavior on the junction temperature of LEDs
could be monitored by a voltmeter in real time. The other concept is modulating the heat energy accumulated inside
LEDs' junction by a heat dissipation module in real time. Therefore, with these physics concepts of LEDs, the effective
method for controlling light emission of LEDs is implemented well by an aid of the feedback control mechanism. The
results show the performance on the light-emission characteristics could be controlled to keep as a steady state, including
optical power, peak wavelength and chromaticity under the feedback control mechanism.
In the work, the light source model for the fluorescence emission
in the biochips has been extensively studied such as to
effectively design the necessary micro-optic elements for the
fluorescence signal detection in biochips. With most advantaging
properties, the fluorescence technology does provide the high
sensitivity, response in real time, and multiple target labeling
for the applications in biochips. To practical applications, the
final signal detection is to measure the fluorescence emission. In
fact, the fluorescence emission process can be determined through
four stages of transformation; that is the excitation, the
absorption, the fluorescence conversion, and the fluorescence
scattering. As the total internal reflection configuration for the
fluorescence excitation is utilized, the evanescent waves are
introduced from different excitation sources in the viewpoints of
the principle analysis and the practical applications,
respectively. In such a way, the spatial intensity of the fluorescence emission is found not to be uniformly distributed,
and the performance of the micro-optic detection system thus
diversed deviated. Except that, the fluorescence emission is
further considered to include the extinction ratio and the quantum
yield of the fluorescent dyes and the scattering effect from the
molecules in the reaction solution. To the end, the precise
fluorescence emission model in the microstructure has been
obtained through the above 4 stages by the optic ray-tracing
simulation. Accordingly, one corresponding collimating lens has
been designed based on the new light source model.
Recently, the applications of light emitting diodes (LED) in illumination are up roaring, and the solutions with high color rendition under various color temperature are in urgent need. Therefore, an effective method for improving lighting properties is very critical and necessary. To study new material of phosphor to combine with the LED chip or new LED structure to emit different spectrum could improve them. In addition, to combine with different kind of LEDs could achieve the same purpose and even with much lower cost. In this work, it has developed such an optimization method for a common white LED combined with a color LED. This method allows for finding the optimal mixing ratio of luminance of both LEDs in order to obtain the best CRI for illumination. By combining with a specific color LED, a white LED whose color temperature is approximately 6500K and CRI is 70, can be improved its color rendering index better than 80 and its correlated color temperature down to near 3000K simultaneously. Moreover, it could produce one which is more close to the warm-white lighting, and it is possible to substitute for the incandescent lamp. Thus, the mixing light is more suitable for illumination in housing applications. In the same way, with more LEDs in combination, CRI could be enhanced much better.