On-machine measurement and characterization of V-groove structure pattern on precision rollers

Rolling imprint lithography is an enabling technique for the mass production of ultra-precision micro-structured surfaces which are widely used in high value added optical products such as backlight guides for display devices. The accuracy of the produced micro-structured surfaces relies heavily on the master roller of which quality is difficult to be controlled by traditional off-line measurement process due to the large dimension and heavy weight of the workpiece. This paper presents a CCD based non-contact measurement system to perform the on-machine measurement of the structure pattern on machined rollers. Instead of measuring each single structure on the roller, the system is more focused on the characterization of the conformance of the structure pattern with the designer's requirement. Low angle monochromatic light is used to extract the structure pattern on the machined roller using a high magnification objective lens with a high resolution CCD sensor. The image processing techniques are then employed to characterize the captured image based on the designed pattern structure. The developed system has been mounted on a single-point diamond turning machine to measure the machined structured roller, and the results indicate that the developed measurement system is able to perform the on-machine measurement and characterization of the structure pattern of the machined roller with sub-micrometre accuracy.