A color target has been designed and fabricated for off-axis illumination reflectance microscopy that utilizes microlens arrays and color mirrors. The color mirrors are optical interference coatings that are similar to designs used for anti-counterfeiting effect pigments. This system of microlenses and color mirrors allows the user to image different colored specular highlights. An infinite number of spectral reflectance profiles can be created with these color targets and used not only colorimetrically, but also for multispectral imaging applications. The targets are not limited to the visible region; they can also be designed to work in the ultraviolet and infrared wavelength regions. This paper will describe how these targets work, the image capturing considerations (flat-fielding, white balance, etc.), and some experimental results.
Jennifer D. T. Kruschwitz, Roy S. Berns, "Imaging Color Target for Off-Axis Illumination Reflectance Microscopy" in Proc. IS&T 22nd Color and Imaging Conf., 2014, pp 247 - 252, https://doi.org/10.2352/CIC.2014.22.1.art00044