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We propose a passive indirect light collector system for interior lighting with the use of diffuse reflectors. This system is based on the idea that diffuse reflectors may increase the acceptance angle of passive systems therefor improving the overall effectiveness and also achieving a better response to light directionality in certain hours of the day. We search the most efficient way to collect optical power by scaling the collection area with a multi-level configuration. We also analyse the light collection on buildings facades through the simulation of the behaviour of the system under cloudy day conditions showing these systems as a feasible and economic option for indirect and direct light collection for interior lighting, allowing a less invasive way to conduct light to interiors with acceptable efficiency and avoiding the use of heliostats or expensive coating materials.

We describe diamond-turned material tests for the integral field unit (IFU) for the FRIDA instrument (inFRared Imager and Dissector for the Adaptive optics system of the Gran Telescopio Canarias). FRIDA is closely based on the design of the successful FISICA cryogenic infrared image slicing device, which used "monolithic" mirror arrays, diamond turned into single pieces of metal. FRIDA, however, will require better roughness characteristics than the 15nm RMS of FISICA to avoid light scatter in FRIDA's shorter wavelength limit (900nm). Al 6061 seems to be limited to this roughness level by its silicate inclusions so some new combination of materials that are compatible with FRIDA's Al 6061 structure must be found. To this end, we have tested six diamond-turned mirrors with different materials and different platings. We used the Zygo interferometer facility at IA-UNAM to do warm and cold profile measurements of the mirrors to investigate possible bimetallic deformation effects. We present a detailed comparison of the various performance characteristics of the test mirrors.