A Novel Experimental Approach for Thermal Stress Measurement in Elastomerically Mounted Optics of Head-Up Display System

Head-up display (HUD) is an opto-electro-mechanical system being used in the cockpit of aircrafts as a see-through display. Mounting and stability of optical components are critical to the opto-mechanical design of high performance display systems. The self-weight deflections and widely varying coefficient of thermal expansion (CTE) between components of field flattener lens mount (FFL) can lead to the development of stress that is subjected to large changes in temperature resulting in lens cracking or catastrophic failure without application of any mechanical load. Therefore, in terms of performance, reliability and cost of the system, it is very important to know the stress developed in the lens. This paper aims at providing a state-of-the-art experimental thermal stress analysis of elastomerically mounted optics. The major research methodologies developed in each of these aspects are presented with detail. From the investigation of stress results, experimental stress values correspond to 80%-90% range with analytical solution and numerical analysis results. So an alternate hypothesis was accepted from the validation of the results. Interestingly, the thermal stress developed in the FFL lens remained intact without exceeding the applicable tensile stress tolerances based on Crompton's suggestion. Hence, the reliability and quality are assured for optical mounts in head-up display and similar systems for aircraft application.