The cantilever beam type of PEH (piezoelectric energy harvester) has been widely studied for years due to simple design and effectively generate high strain and high ouput power. In our previously researches, the PEH unit with area of 6 mm by 9 mm has output performance around 300 μW under base excitation of 0.5g acceleration level. Moreover, we have designed the tapered shape cantilever beam of PEH for optimizing the beam strain distribution and verified that the output performance and durability are not inferior to rectangular one we have fabricated before. In this study, the tapered shape cantilever beam PEHs are chosen for durability experiment to investigate the relevance among output performance, fatigability and mechanical properties of devices with a long-term working period under different working temperature. The result evidently shows the durability difference when the device is operated under high temperature (50°C) with significant natural frequency drop and the PEH could not maintain constant power output.
KEYWORDS: Light emitting diodes, Light sources and illumination, 3D acquisition, LED backlight, Waveguides, Microlens, Light sources, Solid state lighting, LCDs, General lighting
In recent years, LEDs were applied to general lighting in large volume, mostly in territory of backlight lighting.
Therefore, our research would focus on backlight lighting.In this paper, one method was adopted to obtain freeform
surface with non-axial symmetry. Then by the freeform lens constructed by us, we would make the light field intensity
more uniform. At the second part of the paper, we would utilize heterogeneous micro lens array (MLA) to approximate
the shape of the freeform lens, and adjust the curvature radius and size of the micro lenses, and the arrangement way of
the micro lens by the simulation results. Through repeated trials, we could achieve a uniformlight intensity of LEDsusing
microlenses and the thickness of direct-lit backlight unit is 2 mm thick.
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