Communications: directive radio wave systems and devices (e.g. – Directive – Position indicating
Patent
1993-01-19
1994-08-16
Issing, Gregory C.
Communications: directive radio wave systems and devices (e.g.,
Directive
Position indicating
3561411, G01S 302, G01B 1126
Patent
active
053390881
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a method and apparatus for a measurement of the direction, from a position at which the measurement is made, of an observed object or target, such measurement being comparable with directional measurements made with the use of a theodolite.
A conventional theodolite comprises a telescope, mounted to be rotatable about vertical and horizontal axes, and horizontal and vertical circular scales against which the angular position of the telescope can be measured, after it has been aligned on a remote target, to give a first reading related to the bearing or azimuthal direction of the target from the theodolite location and a second reading representing the elevational angle of the target above or below the horizontal. Such a theodolyte requires the co-operation of a human observer, both for aligning the telescope on the target and for reading the azimuthal and elevational data from the circular scales.
It is an object of the present invention to provide a method and apparatus by means of which such azimuthal and elevational data with respect to a suitable remote target can be obtained automatically, that is, without reliance on a human observer. A "suitable" target, for the purposes of the invention, is one which is, effectively, a point source of electromagnetic radiation, preferably but not necessarily in the visible or IR part of the spectrum. In practice, at a range in excess of about 3 meters even an ordinary torch bulb qualifies as a suitable target.
According to one aspect of the invention there is provided a direction-measuring instrument for measuring the direction of a remote source of radiation, the instrument comprising a support, a detector head rotatably mounted thereon for rotation about a fixed axis, and a position-indicator means which provides an output signal indicating the rotational position of the a detector head, the detector head being provided with detector sensitive to radiation emitted by the remote source and with optics for forming an image of the source which transits across the detector as the detector head rotates, the optics being such that the image comprises two line-image components which extend transversely to the transit direction and which are oppositely inclined to that direction, and the detector being arranged, in response to the transit across it of each line-image component, to cause the instantaneous angular position of the detector head as indicated by the position indicator to be recorded, there being further provided computor means which derives two component measurements of the direction of the source from, respectively, the mean of the two recorded angular positions and the difference between them.
In one embodiment of such a direction - measuring instrument according to the invention, the optics for forming an image comprises a pair of elongate cylindrical lenses mounted with their long axes oppositely skewed relative to the axis of rotation of the detector head and forming, of a distant source, correspondingly oppositely skewed line images which transit across the detector as the detector head rotates.
In another embodiment, the optics for forming an image comprises a pair of elongate concave cylindrical mirrors mounted with their long axes oppositely skewed relative to the axis of rotation of the detector head and forming, of a distant source, correspondingly oppositely skewed line images which transit across the detector as the detector head rotates.
According to another aspect of the invention there is provided a method of measuring the direction of a remote source of radiation comprising, in fixed relationship to one another and rotatable together about a fixed axis, a detector sensitive to the radiation emitted by the source and image-forming optics, forming an image of the remote source, the image comprising two line-image components oppositely skewed with respect to the fixed axis, rotating the detector and the image-forming optic together about the fixed axis and thereby causing the two line-image components of the image to tr
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Dudley James R.
Gorham Barry J.
British Technology Group Ltd.
Issing Gregory C.
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