Study and Evaluation of Existing Techniques for Measuring Aircraft Windscreen Optical Quality: Development of New Techniques for Measuring Aircraft Windscreen Optical Distortion

摘要

A program to study and develop techniques for evaluating windscreen optical quality was conducted in support of the Aerospace Medical Research Laboratory's windscreen program. The bird impact resistant transparency (BIRT) windscreens under study were both thick and lightweight laminated components developed to reduce the threat to low-flying aircraft from bird impact. Visual performance is affected by several optical variables of the windscreens; however, this program addressed only the techniques used to evaluate optical distortion. Results of the study indicated that grid board photographic techniques are simple and easy to perform, but errors as large as 20% occur in manual data reduction. Point-by-point measurement of F-111 windscreen optical distortion has shown that this technique provides high accuracy, but is very time consuming. Point-by-point measurements of four representative F-111 windscreens have shown that angular deviations will not usually exceed 40 minutes of arc and that localized optical distortion effects are characterized by large, highly localized variations in angular deviations. Techniques using raster-scanned laser probe beams in conjunction with retro-reflecting screens and holographic lenses could provide the capability for high-speed evaluation of optical distortion in windscreens. The technique to be developed for quantified evaluation of optical distortion should be a grid board photographic system. A grid board digitization system is described to eliminate data reduction errors. (Author)