Browsing by Author "Lee, Xuan-Hao"

Now showing 1 - 4 of 4

Design of a Bicycle Head Lamp Using an Atypical White Light-Emitting Diode with Separate Dies
(2019-12-01)
Lin, Hsin-Jung
;
Sun, Ching-Cherng
;
Wu, Chi-Shou
;
Lee, Xuan-Hao
;
Yang, Tsung-Hsun
To the best of our knowledge, this is the first demonstration of a design for a bicycle head lamp with a high-contrast cutoff line using an atypical white light-emitting diode (LED) with two separate dies. The precise optical model was created by setting the weighting factor on the emitting surface. The downward reflector was designed and fabricated to produce a high-contrast cutoff line in both short- and long-axis orientations, but a yellowish outer pattern was observed. A modified two-color optical model was created to describe the yellowish patterns in both orientations and explain the yellowish effect. Such an effect was caused by the larger coverage area of the phosphor than that by the blue dies. To reduce the yellowish effect near the cutoff line, a specific phosphor area was blocked in the experiment. The yellowish effect was greatly reduced, and the contrast across the cutoff line was enhanced. The presented technology is useful for designing a high-contrast light pattern with such an atypical white LED.
Design of an LED Spot Light System with a Projection Distance of 10 km
(2019-10-01)
Wu, Chi-Shou
;
Chen, Kuan-Yu
;
Lee, Xuan-Hao
;
Lin, Shih-Kang
;
Sun, Ching-Cherng
We designed a spot light system with an illumination range of 10 km. In the designed system, an appropriate white light-emitting diode (LED) was selected according to the exitance and injection power required. Subsequently, through a first-order optical design, the geometry of the lens and reflector was determined using geometrical calculation. Because the central illuminance of the projection spot of the reflector was 2.5 times that of the cover lens, we first considered the fabrication error of the reflector. According to the adjustment of the optimized distance between the white LED and reflector, we modified the design of the cover lens to fit the new location of the white LED. An LED spot light module containing 16 spot light units was used. The module's power injection was only 68.2 W. Because of the excellent performance of the designed system in terms of the divergence angle of the projection beam and maximum luminous intensity, which were 1.6 degrees and 2,840,000 cd, respectively, the projection distance of the LED spot light module was 3.37 Km, according to the ANSI regulation. Finally, a spot light system with nine modules and capable of achieving a projection distance of 10 km was successfully fabricated.
Illuminance and Starting Distance of the Far Field of LED-Array Luminaire Operated at Short Working Distance
(2020-05-01)
Sun, Ching-Cherng
;
Lin, Yi-Syuan
;
Yang, Tsung-Hsun
;
Lin, Shih-Kang
;
Lee, Xuan-Hao
A luminaire with a light-emitting diode (LED) array can provide hotspot illumination in a short range. Therefore, a design of a luminaire with the largest central illuminance (LCI) and a high uniformity is warranted. In this paper, we present a study of illuminance variation with respect to the distance of an illumination target of a luminaire with LED array. The emission property of the luminous intensity is characterized by the cosine power law or the divergent angle of full width at half maximum (FWHM). A real LED module is designed to create the simulation for different luminaire types. The occurrence of the LCI and the far-field region are observed. Our results demonstrate that the LCI distance remains shorter than the starting distance of the far field (SDFF). To simplify the simulation, we propose the replacement of the real LED module with a point or flat-extended source. Such light sources must be equipped with the specific cosine power factor corresponding to the divergent angle of the FWHM of the LED module. These light sources are acceptable for describing illumination characteristics, including the SDFF. Our results may facilitate the design of LED-array luminaires operated at short working distances, such as reading lighting or illumination in microscopes.
Method of compensating for pixel migration in volume holographic optical disc (VHOD)
(2012-09-10)
Yu, Yeh-Wei
;
Cheng, Chih-Yuan
;
Teng, Tun-Chien
;
Chen, Cheng-Hsien
;
Lin, Shiuan-Huei
Volume holographic optical disc (VHOD) technology is simpler than the angular multiplexing holographic system. However, disc rotation usually causes pixel migration, thus reducing signal quality. This study proposes a special geometrical arrangement to counteract pixel migration. Using paraxial approximation analysis, an optimal geometrical distance ratio, K, is calculated to compensate for pixel migration and improve image quality during disc rotation. The results of approximation analysis are confirmed by both simulation and experimental results. (C) 2012 Optical Society of America