The secondary research process involved comprehensive analysis of regulatory databases, industry standards, technical publications, and authoritative technology organizations. Key sources included the US Federal Communications Commission (FCC), National Institute of Standards and Technology (NIST), US Department of Energy (DOE) Office of Energy Efficiency & Renewable Energy, European Telecommunications Standards Institute (ETSI), International Electrotechnical Commission (IEC), Society for Information Display (SID), Consumer Technology Association (CTA), IEEE Xplore Digital Library, US Patent and Trademark Office (USPTO), European Patent Office (EPO), Japan Patent Office (JPO), Organization for Economic Co-operation and Development (OECD) Digital Economy Outlook, International Data Corporation (IDC), National Science Foundation (NSF) Technology Statistics, and national technology ministry reports from key markets including China's Ministry of Industry and Information Technology (MIIT), Japan's Ministry of Economy, Trade and Industry (METI), and South Korea's Ministry of Science and ICT. These sources were used to collect technology standards, patent landscapes, regulatory compliance data, shipment statistics, adoption trends, and competitive landscape analysis for volumetric displays, stereoscopic displays, head-mounted displays, and underlying technologies including OLED, DLP, PDP, and LED.