Optical tools offer a route to increasing throughput and efficiency in industrial inspection operations, one of the most
time-consuming and labour-intensive aspects of modern manufacturing. One prominent example in the medical device
industry is inspection of drilled holes, particularly in narrow-bore tubes (precision-flow devices, such as catheters for
drug delivery, radio-opaque contrast agents, etc). The products in which these holes feature are increasing in complexity
(reduced dimensions, increasing number of drilled features- in some products now reaching into the hundreds). These
trends present a number of technical challenges, not least to ensure that holes are completed and that no damage to the
part occurs as a result of over-drilling, for example. This paper will present a novel sensor based on back-side
illumination of the drilled hole using side-glowing optical fibers to detect, qualify and quantify drilled holes.
The concept is based on inserting a laser-coupled side-glowing optical fiber into the lumen of the tube to be drilled, and
imaging the light emitted from this fiber through a drilled hole using a vision system mounted external to the tube. The
light from the fiber allows rapid determination of hole completion, shape and size, as well as quantity in the case of
products with multiple holes. If the fiber is mounted in the tube prior to drilling, the light emitted from the fiber can be
used as a real-time hole breakthrough sensor, preventing under or overdrilling of the tube.
The aim of this work is to investigate the application of the spectral reflectance technique to thickness measurement of highly localised semi-transparent coatings on miniature geometries, such as those used in the medical devices industry. The paper will describe the application of the technique to coatings on curved or non-uniform surfaces such as narrow-bore metal tubes and thin wires. The paper will describe the equipment used including a spectrometer with micro-focus attachment, and optical modelling software. This work also involved laser-drilling of the polymer films to allow complementary step-height measurements to be made. Special steps were also required to overcome problems in measurement due to the transparency of the thin films. Complementary techniques including white-light interferometry, which were used to benchmark the method, will also be described.