With the advantages of low cost, small volume, low energy consumption, long service life and environment friendly, the
application of UV-LED has attract widespread concern among academia and industry researchers, especially in the field of
ink printing industry. However, how to get high power density in specific distance working plane is a technical problem
need to be solved eagerly. This paper presents a design solution to reduce the Etendue of the lighting system and therefore
obtain high power density. The design uses UV-LED array as the light source, and uses a freeform surface collimating lens
array to collimate this light source. In order to improve the energy sufficiency of the system, multipoint fitting-based
freeform surface lens design for UV-LED extended sources is proposed to design collimating free-form lens for UV-LED
extended source in this work. The freeform surface collimating lens array is placed in front of the UV-LED extended
sources array. And an aspherical lens is used in the optical path to focus the light beam. In the simulation, a light source
module with the size of 9mm * 26mm has been designed, and obtained power density up to 8W/cm2 in the specific working
plane with the working-distance of 3cm. This design is expected to replace the existing mercury lamped-based UV light
sources and solve the problem in the application of UV-LED ink printing field.
Organic light emitting diode (OLED) is a typical surface source with continuous luminous area. It is important to know its far-field condition since most of lighting designs are based on the far-field characteristics. In this paper, the relative far-field distances (RFFD) for OLEDs with round, rectangular, annular, hemispherical and semi-cylindrical shapes are calculated. The RFFDs for LED arrays with the same shapes are also given for comparison. Results show that the RFFDs for OLEDs are smaller than that of LED arrays with the same shapes and sizes for most situations.
If a surface light source is in far-field working condition, the error from using the inverse-square law about intensity and distance should be less than 1%. However, the results of where the far-field begin may be quite different with different error definition. In this paper, by comparing several formulas commonly used for error analysis, the root mean square (RMS) weighted by the sum of intensity at infinity is proposed as the preferred error formula for far-field distances calculation. The relative far-field distances (RFFDs) for LED arrays with different radiation pattern are calculated based on this error definition.
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