The Research Of LED-based Spectrally Tunable Source

Recently, advance in materials and manufacture area has resulted in the commercial availability of light emitting diode (LED) with high luminance and wide spans of the dominant wavelengths within the entire visible spectrum. Because of the narrow spectral distribution, if the kind of LEDs available is enough for the spectrum span of specific target source, it is possible to make a spectrally tunable light source that is able to provide a high fidelity spectral match to a spectral power distribution.Considered the need of laboratory radiometric calibration, this thesis introduced the theory of integrating sphere , analyzed and summarized the shortcomings of the radiometric calibration source in use at the present time . Then the optical and electrical characteristics of LED were discussed including the driver circuit .The feasibility of spectrally tunable LED-based light source was verified. The source is capable of producing any spectral distribution. According to the measured LED spectral distribution, an asymmetric Gaussian function model was proposed to fit the individual LED spectral distribution. A variety of different LEDs with different peak wavelengths were utilized to synthesize the required spectral distribution. In theory, the least square fitting for any spectrum is realized. The experimental results of synthesis of typical spectral distribution are satisfactory. Finally, based on the analysis of experimental data, this paper put forward some points for the engineering practice. It is also possible to prducing target spectral distribution with white LEDs, if the monocolor LEDs with specific peak wavelengths are not available.