GB1280441A - Improvements in or relating to horizon sighting sensors - Google Patents

Abstract

1280441 Horizon detector BARR & STROUD Ltd 29 Dec 1970 [6 Jan 1970] 695/70 Heading H4D [Also in Division G2] A horizon sensor comprises a double-sided mirror 11 oscillated about a horizontal axis 13 and a detector 12, an infra-red image received through lens 10 being scanned by mirror 11 and detector 12. The signal from the detector 12 is fed to a light source 14 which is energized when the discontinuity between the infra-red received from the sea and the sky is detected. The light from source 14, which may be a point source, is reflected from mirror 11 and through a lens 15 astigmatizing lens 16 to give a line image of the horizin. The sensor of Fig. 1 may be incorporated into a sectant to provide a horizon image in darkness. The mirror 11 may be one-sided, the light from source 14 being reflected from the same side of the mirror as the received infra-red radiation, a prism then being included between mirror 11 and lens 15 so that the resultant light is parallel to the radiation incident on lens 10. The mirror 11 may be replaced by a rotated multi-sided prism. In order that the horizon line image may be horizontal irrespective of the orientation of the sensor the lenses 15 and 16 may be pendulously mounted. The lens 16 may be dispensed with, a pendulously mounted diaphragm having spaced parallel slits then being provided at source 14, or a pendulously mounted strip light being used as source 14. The source 14 may be continuously energized, the detector 12 then controlling a shuttering arrangement. To correct for any time delay between detection of the horizon discontinuity and operation of the source 14 two light sources may be used to produce images above and below the true horizon, or the sensor may be arranged to produce these two images from one light source. A pendulously mounted graticule may be associated with the light source to provide the horizon line.