device to make light marks on the optical path of the observation aircraft at night

摘要

1532401 Night sights SIEMENS-ALBIS AG 16 June 1977 [17 June 1976] 25165/77 Heading H4F A night sight includes a transparent plane parallel plate 5 carrying a reference sighting marking 8, the plate being mounted normal to the optical axis of the sight. The marking is illuminated by a beam of light projected into the plate through its rim so that the central component of the beam meets the axis of the sight at the centre K of the marking and at such an angle relative to the face of the plate that total internal reflection takes place, except where the beam meets the marking, so rendering the marking luminescent against a dark background. The beam may be formed by use of an l.e.d. 10 and masks 12, 13. Light guides (26) may lead the light from one mask (23) to the other (24), Fig. 4 (not shown). The apertures in the masks may be elliptical. The beam-forming unit may include a sky filter (25).