Advanced Head-Up Display System for Closed Circuit Rebreathers

U.S. Navy Special Warfare (NSW) and Explosive Ordnance Disposal (EOD) Divers perform critical underwater missions while diving Closed Circuit Rebreather Underwater Breathing Apparatus (CCR-UBAs). Military CCR-UBAs are typically back-worn, electronically controlled, mixed gas diving systems with the oxygen in the diver's breathing gas mix monitored and controlled via a battery-powered electronic module. Two separate electronic visual displays monitor the status of the rebreather with oxygen and diluent bottle pressures monitored on two separate analog pressure gauges. The electronic visual displays are comprised of a primary display module (PDM) and a secondary display module (SDM). The PDM connects to the CCR-UBA electronics module via a cable and is a simple series of red and green light emitting diodes (LEDs) that alert the diver to any equipment malfunctions or warnings. The PDM attaches to the dive mask on the upper right or left side, or to the regulator slightly below the diver's normal field of vision. The SDM is an alphanumeric liquid crystal display (LCD) handset that displays detailed data on oxygen sensor voltages, and batteries' status. It connects to the CCR-UBA electronics module via a separate cable. Depth is monitored on a separate depth gauge. During dive missions in high turbidity and zero visibility conditions (which is very common in military dive missions), the diver is unable to see the critical information on the SDM, oxygen and diluent gauges, and the depth gauge. Under a project funded by the Combating Terrorism Technical Support Office (CTTSO), the Naval Surface Warfare Center-Panama City Division (NSWCPCD) developed two (2) concept prototype systems that fully integrate the critical CCR-UBA display data into a single head-up display capability, clearly visible by the NSW/EOD diver even in high turbidity and zero visibility conditions. The paper will describe the different design approaches taken for the two different prototype systems developed, use of additive manufacturing/3D printing to design and build the prototypes, the unique optical system design, and results of design reference mission testing by military divers.