We present the design and realization of an imaging system intended for use as a reference method for the accurate measurement of cotton fiber length. The prototype system is composed of an off-the-shelf scanner that generates a grayscale image of multiple individualized fibers, followed by customized image processing algorithms that compute the length of each fiber in the image. Although the system requires some degree of separation between the individual fibers at scan time, it is shown to produce highly accurate length measurements that are invariant to fiber orientation, shape, interfiber intersections, and intrafiber crimps and crossovers. Hence, in its present state, the proposed system serves as an excellent reference method for assessing the efficacy of commercially available length measurement systems. 2008 SPIE and IS&T.