GB870557A - Improvements in or relating to optical device - Google Patents

Abstract

870,557. Visual landing aids for aircraft. BURROUGHS CORPORATION. July 25, 1958 [July 25, 1957], No. 24071/58. Class 118. [Also in Group XI] A visual landing aid for aircraft comprises a plurality of optical systems arranged in a substantially vertical array and a horizontally-disposed reference marker adjacent thereto, each optical system comprising a lens and a light source arranged within the focal distance of the lens and the optical system being so arranged that the axes of the beams of adjacent systems diverge in the vertical plane, that of the uppermost system being at a steeper angle and that of the lowermost system being at a shallower angle than the desired glide plane, whereby the pilot of an approaching aircraft sees a virtual image of one of the light sources whose position relative to the reference marker indicates his angular position with respect to the desired glide plane. As shown in Fig. 2B, the reference marker comprises a plurality of lamps 20, the apparent position of the image 25b as seen by the pilot of the approaching aircraft indicating in this instance that the aircraft is above the glide plane. The vertical array of optical systems is mounted as an assembly 30, a lenticular spreader 60, Fig. 5, being arranged in front of the optical system to spread the image out into a horizontal band. The assembly 30 comprises five optical systems, each comprising a fresnel lens 50 and four lamps 40, lying along a horizontal arc conforming with the curvature of the field of the lens 50. The different optical systems are all so arranged, either by inclination of the axes of the lenses 50 or by displacement of the lamps 40 therefrom that the virtual images produced thereby all coincide. Hence an observer in front of the array sees only one image, whose position with respect to the array appear to depend on his angular disposition with respect thereto. The vertical positions of the filaments of the lamps may be individually adjusted by screws 68 and when the apparatus is to be used on an aircraft carrier the lamps are all mounted on a common support which may be moved vertically by a gyroscopically controlled motor 43 for stabilizing the beams of the optical systems. When the support moves vertically cam followers 64 move over corresponding cam surfaces 66 to alter the spacing between the corresponding lamps 40 and lenses 50 in accordance with the curvature of the field of the lenses. The inclination of the array in the vertical plane may be adjusted by hand wheel 39 operating through gearing 38; alternatively the gyroscopic stabilizing means may operate on gearing 38 in which case motor 43 may be dispensed with. Specification 758,273 is referred to.