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Since mechanical accuracy is of major importance in the field of optics, piece production is still prevailing and implementations of techniques of mass production are a challenge. Using injection molding of plastic elements onto sheet metals (e.g. so-called OUTSERT-technology) provides a new approach to resolve this issue. Clearly, such a technique could save spacers and retainer rings as well as process time in assembly and allow an economical production of optics mounts at high production rates, if the required mechanical accuracy can be met. For a mobile projection application, the lens barrel of a fix-focus projection lens has been realized in this technology. The design is based on a segmented lens cage with fixed and loose plastic bearings parts for each optical element. Important for accurate lens alignment is a 3-fold symmetry of the cage. Due to the symmetrical layout, reproducibility of the injection molding process is of greater importance than absolute mechanical accuracy. A careful characterization of the constituent parts has been performed, using non-contacting 3d-shape measurements. The data obtained so far reveal satisfying results with respect to reproducibility and selected dimensions of the lens seats. Also, tilt deviations of the lens surfaces in the assembled mount were determined. Further, a preliminary measurement of the Modulation Transfer Function (MTF), to check the optical performance, has been obtained and shows encouraging results.
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