Using the technology landscape in Fig 1, we find there are approximately 19,000 patents with the words 'light' and guide' and 'plate' in the title or the abstract. Each patent is classified with one or more International Patent Classifications (IPCs). For example, IPC G02B6/00 includes: "Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings". 3,726 of these 19,000 patents are classified as being in this category. We can identify which category, or categories, the technology will fall into, and see how many patents are already filed in that sector.