RESUMEN
A cost reduced method of producing injection molding tools is reported and demonstrated for the fabrication of optical microlens arrays. A standard computer-numerical-control (CNC) milling machine was used to make a rough mold in steel. Surface treatment of the steel mold by spray coating with photoresist is used to smooth the mold surface providing good optical quality. The tool and process are demonstrated for the fabrication of an ø50 mm beam homogenizer for a color mixing LED light engine. The acceptance angle of the microlens array is optimized, in order to maximize the optical efficiency from the light engine. Polymer injection molded microlens arrays were produced from both the rough and coated molds and have been characterized for lenslet parameters, surface quality, light scattering, and acceptance angle. The surface roughness (Ra) is improved approximately by a factor of two after the coating process and the light scattering is reduced so that the molded microlens array can be used for the color mixing application. The measured accepted angle of the microlens array is 40° which is in agreement with simulations.
RESUMEN
The miniaturization of surface-scattering instruments for measuring viscoelastic properties is investigated. The concepts are based on the use of holographic optical elements and integrated optics. Compact forms of optics that provide the necessary spatial and angular selections are devised. Four systems representing increasing levels of integration are considered. It is demonstrated that efficient signal and data processing can be achieved by evaluation of the statistics of the derivative of the instantaneous phase of the detector signal.