Design, tolerancing and fabrication of a freeform lightguide based on the flow-line method

We present a miniature freeform lightguide for sensing applications, designed according to the principles of the flow-line method from Nonimaging Optics. The optic is obtained by combining two 2D flow-line concentrators in a curved monolithic piece, achieving 45 degrees half-acceptance angle and 40 degrees beam steering in a very compact volume (about 1.3 x 2.0 x 20 mm(3)). We show how the initial design has been adjusted after a thorough tolerance analysis and describe its fabrication through plastic injection molding. The design of the mold involves a non-standard 3D-puzzle approach, which allows uniform high optical quality and minimizes the fillet radius on the optic.