Abstract: A method and apparatus are provided for determining the orientation of an object relative to a platform likely to be exposed to buffeting. The object may be a helmet worn by a pilot in which orientation of the helmet relative the aircraft while in flight may usefully be known, in particular when determining the position of space-stabilised symbols being displayed in an associated helmet-mounted digital display system. According to the method, not only may orientation of an object may be predicted at some time ahead of a time point of validity of source sensor data, but the prediction may be dynamically configured to according to a detected severity of buffeting to reduce the effects of the buffeting upon the quality of data output by the system. The method includes measuring the severity of any buffeting using the same source data as used to determine orientation of the object.

Abstract: A method is provided for determining corrections to rate data output by inertial sensors of a type typically used in tracking changes in orientation of an object. The present invention also extends to a tracker system incorporating the correction functionality of the present invention. The method makes use of rate data output by inertial sensors associated with the object being tracked and rate data derived from measures of orientation supplied by a non-inertial tracker system also associated with the object being tracked and comprises determining from those rate data corrections for errors due to misalignment in rate data output by inertial sensors, by calculating a mapping between vectors linking points in inertial sensor rate space represented by a sample set of received rate data from the inertial sensors and vectors linking points in a derived object orientation rate space represented by a corresponding and synchronised sample set of derived rate data.

Abstract: A method and apparatus are provided for determining the orientation of an object relative to fixed, moving or moveable platform likely to be exposed to buffeting or similar effects. The object may for example be a helmet worn by a pilot of an aircraft in which orientation of the helmet relative the aircraft while in flight may usefully be known, in particular when determining the position of space-stabilised symbols being displayed in an associated helmet-mounted digital display system. According to the method, not only may orientation of an object may be predicted at some time ahead of a time point of validity of source sensor data—a useful feature for digital display systems—but the functionality carrying out the prediction may be dynamically configured to according to a detected severity of buffeting upon the object and upon the tracker system sensors to reduce the effects of the buffeting upon the quality of data output by the tracker system.

Abstract: A method and apparatus are provided for determining the orientation of an object relative to a moving or moveable platform. The object may for example be a helmet worn by a pilot of an aircraft in which orientation of the helmet relative the aircraft while in flight may usefully be known, in particular when determining the position of space-stabilised symbols being displayed in an associated helmet-mounted digital display system. The method and apparatus rely upon a combination or orientation rate data output by an inertial sensor arrangement associated with the object and orientation data output by a non-inertial tracker system associated with the object. Orientation data of the moveable platform is also used to reference the non-inertial tracker output to inertial space.

Abstract: A method and apparatus are provided for determining the orientation of an object relative to a moving or moveable platform. The object may for example be a helmet worn by a pilot of an aircraft in which orientation of the helmet relative the aircraft while in flight may usefully be known, in particular when determining the position of space-stabilised symbols being displayed in an associated helmet-mounted digital display system. The method and apparatus rely upon a combination or orientation rate data output by an inertial sensor arrangement associated with the object and orientation data output by a non-inertial tracker system associated with the object. Orientation data of the moveable platform is also used to reference the non-inertial tracker output to inertial space.

Abstract: A method is provided for determining corrections to rate data output by inertial sensors of a type typically used in tracking changes in orientation of an object. The present invention also extends to a tracker system incorporating the correction functionality of the present invention. The method makes use of rate data output by inertial sensors associated with the object being tracked and rate data derived from measures of orientation supplied by a non-inertial tracker system also associated with the object being tracked and comprises determining from those rate data corrections for errors due to misalignment in rate data output by inertial sensors, by calculating a mapping between vectors linking points in inertial sensor rate space represented by a sample set of received rate data from the inertial sensors and vectors linking points in a derived object orientation rate space represented by a corresponding and synchronised sample set of derived rate data.

Abstract: A user (18) views a reference symbol (36) along a line of sight (28) intersected by an image intensifier (22), arranged to present an intensified image of a forward scene (26) to the eye (24) of the user (18), and an image display (14), arranged to display an image to the eye (24) of the user (18) overlaid on the intensified image. The user indicates alignment of first and alternate symbols generated at known positions on the image display (14) with the reference symbol (36) and the position of a helmet (16) carrying the image display (14) is determined by a helmet tracking system (30) for each alignment. A line of sight can be determined for each symbol alignment given the helmet (16) position and known location of the first and alternate symbols. These lines of sight can be used to determine the magnification factor of the forward scene (26) induced by the image intensifier (20).

Abstract: A method and system of aligning a helmet mounted display mounted to a helmet is disclosed. A method may comprise aligning a first and a second helmet mounted display guide symbol with a reference direction, respectively; selecting the alignment of the first and second helmet mounted display guide symbol with the reference direction, respectively; aligning a first and a second stabilised guide symbol, starting at positions of the aligned first and second symbols, respectively, with the reference direction, the first and second stabilised symbols being stabilised to reduce the movement of the stabilised symbol with respect to the reference direction in response to movements of the head of the user; selecting the alignment of the first and second stabilised guide symbol with the reference direction, respectively; determining a relative position and orientation between the helmet and the display according to the positions and orientations of the helmet at the alignments.

Abstract: A user (18) views a reference symbol (36) along a line of sight (28) intersected by an image intensifier (22), arranged to present an intensified image of a forward scene (26) to the eye (24) of the user (18), and an image display (14), arranged to display an image to the eye (24) of the user (18) overlaid on the intensified image. The user indicates alignment of first and alternate symbols generated at known positions on the image display (14) with the reference symbol (36) and the position of a helmet (16) carrying the image display (14) is determined by a helmet tracking system (30) for each alignment. A line of sight can be determined for each symbol alignment given the helmet (16) position and known location of the first and alternate symbols. These lines of sight can be used to determine the magnification factor of the forward scene (26) induced by the image intensifier (20).

Abstract: A method and system of aligning a helmet mounted display mounted to a helmet is disclosed.

Abstract: The surface quality of halide, preferably fluoride, articles, e.g., articles used in the preparation of halide fibers is improved by cleaning the surface with an aqueous etchant and thereafter removing the etchant by washing the surface with methanol. The aqueous etchant is preferably a solution which contains hydrochloric acid and zirconium oxychloride.