Micro Collimated Light Source Using Micro Fresnel Lens

Abstract

We have developed super micro collimated light source (MCL) without attaching any other external collimating lens. The MCL is assembled with a light source such as a laser diode (LD) or a light emitting diode (LED) and a micro collimating lens in the smallest commercially available laser package. In order to obtain a compact MCL and narrow and high quality collimated beam, a short focal length micro Fresnel lens (MFL) has been utilized for the first time as the collimating lens. The radiated beam from the MCL using LD light source has higher than 3 mW intensity at 50 mA driving current, narrow enough as φ1.3mm beam diameter with nearly Gaussian intensity profile, and lower than λ/14 (RMS value) wavefront aberration measured at 50cm distance. The beam from the MCL using LED has 0.5 mW intensity at 50 mA driving current and about φ1.6 mm beam diameter as narrow as in the case of LD light source. The MCL has also high reliability against temperature variation and humidity, because all of the elements are assembled in the small package filled with dry N2 gas.