Projection screen device for guidance of a helicopter in flight close to the ground at night

摘要

With the night use of image-amplifying spectacles 4 for observation at 2 by the pilot of the region close to the ground, observation is impaired even by low intensities of scattered light. A display of the instrument readings on a projection screen 8 which does not interfere with observation of the surroundings uses light in or close to the blue region of the visible spectrum. Light having a maximum intensity at wavelengths of about 430 to 480 nm is preferably used. Light in or close to the blue region can be produced or enhanced by using a colour filter 12. It is also possible to use luminous phosphors having all emission maximum at wavelengths of between 430 and 480 nm on the projection screen. The projection screen 8 is conveniently covered by a louvre filter 14, preferably a louvre filter in which louvre elements are directed transversely of the screen. IMAGE