Obstacle avoidance system for helicopters and other aircraft

An obstacle avoidance system for use on an aircraft for sensing objects along the flight path thereof and alerting the pilot to their presence, said aircraft having an avionics system for producing instrumentation data concerning the attitude and the velocity vectors of the aircraft and a video display system for displaying information to the pilot, the system comprising:

• a laser radar subsystem for emitting a beam of laser energy pulses, for receiving returns from objects, and for processing the returns to produce data related to existence of objects in the flight path of said aircraft, said laser radar subsystem including analyzing means for identifying wire-shaped objects and for identifying bulky objects from said returns and for calculating the range and direction information of said objects whenever found;
• a scanning subsystem mounted on the aircraft and operatively coupled to the laser radar subsystem for scanning the beam over a field of regard and producing directional information related to the instantaneous direction of the beam relative to the aircraft;
• said scanning subsystem further including a first scanner for scanning the beam in a circular scan pattern centered on a first scan axis and a second scanner for moving the first scan axis azimuthally in a repetitive motion so that the circular scan pattern covers the field of regard;
• and
• processor circuitry operatively connected to the laser radar subsystem, the scanning subsystem, the avionics system, and the video display system, for controlling operation of the laser radar subsystem and the scanning subsystem, for processing the range data, directional information, and instrumentation data in order to produce a stream of data representing video information related to the range, azimuth and elevation of said objects, and for developing therefrom a line representing the lower limit of safe clearance azimuthal and elevational headings for said aircraft over and around said wire-like objects and bulky objects,
• means for displaying a heading indicator on said display showing the intercept of the projected path of aircraft travel onto said video display,
• means for displaying said line on said video display, the area above said line representing a window of safety for the flight of said aircraft which may then be flown to keep the heading indicator above said line and within said window.

An obstacle avoidance system for use on an aircraft for sensing objects along the flight path thereof and alerting the pilot to their presence, said aircraft having an avionics system for producing instrumentation data concerning the attitude and the velocity vectors of the aircraft and a video display system for displaying information to the pilot, the system comprising:

• a laser radar subsystem for emitting a beam of laser energy for receiving returns from objects, and for processing the returns to produce data related to existence of objects in the flight path of said aircraft, said laser radar subsystem including analyzing means for identifying wire-shaped objects and for identifying bulky objects and for calculating the range and direction information of said objects whenever found;
• a scanning subsystem that is mounted on the aircraft and operatively coupled to the laser radar subsystem for scanning the beam over a field of regard and producing directional information related to the instantaneous direction of the beam relative to the aircraft;
• said scanning subsystem further including a first scanner for scanning the beam in a circular scan pattern centered on a first scan axis and a second scanner for moving the first scan axis azimuthally in a repetitive motion so that the circular scan pattern covers the field of regard;
• and
• processor circuitry operatively connected to the laser radar subsystem, the scanning subsystem, the avionics system, and the video display system, for controlling operation of the laser radar subsystem and the scanning subsystem, for processing the range data, directional information, and instrumentation data in order to produce video information related to the range and direction of said objects, and for interfacing the video information to the video display system for viewing by the pilot
• said processor circuitry being programmed to analyze returns by:
• subdividing the field of regard into a series of analysis windows;
• relating each of the returns to a particular one of the analysis windows from which the return came;
• performing a statistical analysis of the returns related to each of the analysis windows;
• and
• identifying returns that fall into a common range interval.

An obstacle avoidance system for use on an aircraft for sensing objects along the flight path thereof and alerting the pilot to their presence, said aircraft having an avionics system for producing instrumentation data concerning the attitude and the velocity vectors of the aircraft and a video display system for displaying information to the pilot, the system comprising:

• a laser radar subsystem for emitting a beam of laser energy for receiving returns from objects, and for processing the returns to produce data related to existence of objects in the flight path of said aircraft, said laser radar subsystem including analyzing means for identifying wire-shaped objects and for identifying bulky objects and for calculating the range and direction information of said objects whenever found;
• a scanning subsystem that is mounted on the aircraft and operatively coupled to the laser radar subsystem for scanning the beam over a field of regard and producing directional information related to the instantaneous direction of the beam relative to the aircraft;
• said scanning subsystem further including a first scanner for scanning the beam in a circular scan pattern centered on a first scan axis and a second scanner for moving the first scan axis azimuthally in a repetitive motion so that the circular scan pattern covers the field of regard;
• and
• processor circuitry operatively connected to the laser radar subsystem, the scanning subsystem, the avionics system, and the video display system, for controlling operation of the laser radar subsystem and the scanning subsystem, for processing the range data, directional information, and instrumentation data in order to produce video information related to the range and direction of said objects, and for interfacing the video information to the video display system for viewing by the pilot
• said processor circuitry being programmed to transform coordinates of objects measured relative to the aircraft to a horizon-stabilized, north-oriented coordinate system which is independent of the attitude of the aircraft.

An obstacle avoidance system for use on an aircraft for sensing objects along the flight path thereof and alerting, the pilot to their presence, said aircraft having an avionics system for producing instrumentation data concerning the attitude and the velocity vectors of the aircraft and a video display system for displaying information to the pilot, the system comprising:

• a laser radar subsystem for emitting a beam of laser energy for receiving returns from objects, and for processing the returns to produce data related to existence of objects in the flight path of said aircraft, said laser radar subsystem including analyzing means for identifying wire-shaped objects and for identifying bulky objects and for calculating the range and direction information of said objects whenever found;
• a scanning subsystem that is mounted on the aircraft and operatively coupled to the laser radar subsystem for scanning the beam over a field of regard and producing directional information related to the instantaneous direction of the beam relative to the aircraft;
• said scanning subsystem further including a first scanner for scanning the beam in a circular scan pattern centered on a first scan axis and a second scanner for moving the first scan axis azimuthally in a repetitive motion so that the circular scan pattern covers the field of regard;
• and
• processor circuitry operatively connected to the laser radar subsystem, the scanning subsystem, the avionics system, and the video display system, for controlling operation of the laser radar subsystem and the scanning subsystem, for processing the range data, directional information, and instrumentation data in order to produce video information related to the range and direction of said objects, and for interfacing the video information to the video display system for viewing by the pilot
• said processor circuitry being programmed to insert the coordinates of identified objects into a data base so that the coordinates may be used for constructing a video display at a later time.

A system for sensing objects in the flight path of an aircraft and alerting a pilot of the aircraft to their presence, the system comprising:

• means in the form of a laser radar subsystem for emitting a beam of laser energy, for receiving returns from objects, and for processing the returns to produce range data related to the range of the objects from the aircraft, the laser radar subsystem being mounted on an aircraft having means in the form of an avionics system for producing instrumentation data concerning the attitude and the velocity vectors of the aircraft and means in the form of a video display system for displaying information to a pilot of the aircraft;
• means in the form of a scanning subsystem that is mounted on the aircraft and operatively coupled to the laser radar subsystem for scanning the beam over a field of regard and producing directional information related to the instantaneous direction of the beam relative to the aircraft;
• and
• means in the form of processor circuitry operatively connected to the laser radar subsystem, the scanning subsystem, the avionics system, and the video display system, for controlling operation of the laser radar subsystem and the scanning subsystem, for processing the range data, directional information, and instrumentation data in order to produce video information related to the range and direction of the objects, and for interfacing the video information to the video display system;
• the processor circuitry being programmed to overlay the video information on other video information displayed by the aircraft video system;
• said processor circuitry further being programmed to perform at least one of:
• providing acoustical warnings on an aircraft intercom system;
• analyzing returns by subdividing the field of regard into a series of analysis windows, relating each of the returns to a particular one of the analysis windows from which the return came, performing a statistical analysis of the returns related to each Of the analysis windows, and identifying returns that fall into a common range interval;
• transforming coordinates of objects measured relative to the aircraft to a horizon-stabilized, north-oriented coordinate system which is independent of the attitude of the aircraft;
• inserting the coordinates of identified objects into a data base so that the coordinates may be used for constructing a video display at a later time and updating the data base to correct for movements of the aircraft;
• and
• constructing a display of objects currently within the field of regard by adjusting the displayed position of the objects to compensate for avoidance maneuvers the pilot may execute.

A method of scanning a laser beam over a field of regard, comprising:

• providing a scan element in the form of holographic optical element pair together with means for reducing zero order beam bleed-through transmittance therefrom;
• directing an on-axis laser beam with said optical element toward a field of regard in an off-axis direction relative to a first scan axis;
• spinning the optical element on the first scan axis so that the laser beam produces a circular scan pattern within the field of regard that is centered on the first scan axis;
• and
• pivoting the optical element and the first scan axis about a second scan axis that is perpendicular to the first scan axis in order to move the circular scan pattern in a repetitive motion over the field of regard.

A method of scanning a laser beam over a field of regard, comprising

• scanning the beam in a circular scan pattern within the field of regard;
• and
• moving the circular scan pattern repetitively over the field of regard,
• and varying the angular velocity of pivoting the optical element and the first scan axis about a second scan axis that is perpendicular to the first scan axis in response to the turn rate of the aircraft in order to keep the azimuthal scan rate constant with respect to the environment.

A method of scanning a laser beam over a field of regard, comprising:

• directing an on-axis laser beam with said optical element toward a field of regard in an off-axis direction relative to a first scan axis, while directing the on-axis beam in an intermediate direction with a first hologram on the optical element and then directing the beam in the off-axis direction with a second hologram on the optical element;
• spinning the optical element on the first scan axis so that the laser beam produces a circular scan pattern within the field of regard that is centered on the first scan axis;
• and
• pivoting the optical element and the first scan axis about a second scan axis that is perpendicular to the first scan axis in order to move the circular scan pattern in a repetitive motion over the field of regard.

A method of sensing and alerting a pilot to objects in the flight path of an aircraft having an avionics system for producing instrumentation data concerning the attitude and the velocity vectors of the aircraft and a video display system for displaying information to a pilot of the aircraft, the method comprising:

• providing means in the form of a laser radar subsystem mounted on the aircraft for emitting a beam toward objects, for receiving returns from the objects, and for processing the returns to produce range data related to the range of the objects;
• said processing including analyzing returns by subdividing the field of regard into a series of analysis windows, relating each of the returns to a particular one of the analysis windows from which the return came, performing a statistical analysis of the returns related to each of the analysis windows, and identifying returns that fall into a common range interval, and further analyzing to identify wire-shaped objects and to identify bulky objects and calculating the range and direction information of said objects whenever found;
• scanning the beam in a circular scan pattern centered on a first scan axis while moving the first scan axis azimuthally in a repetitive motion so that the circular scan pattern covers a field of regard;
• producing directional information related to the instantaneous direction of the beam relative to the aircraft;
• processing the range data and the directional information with the instrumentation data to produce video information related to the range and direction of said objects;
• and
• interfacing the video information relating to said objects to a video display system on the aircraft.

A method for sensing and alerting a pilot to objects in the flight path of an aircraft having an avionics system for producing instrumentation data concerning the attitude and the velocity vectors of the aircraft and a video display system for displaying information to a pilot of the aircraft, the method comprising:

• providing means in the form of a laser radar subsystem mounted on the aircraft for emitting a beam toward objects, for receiving returns from the objects, and for processing the returns to produce range data related to the range of the objects;
• scanning the beam in a circular scan pattern centered on a first scan axis while moving the first scan axis azimuthally in a repetitive motion so that the circular scan pattern covers a field of regard;
• producing directional information related to the instantaneous direction of the beam relative to the aircraft;
• processing the range data and the directional information with the instrumentation data to produce video information related to the range and direction of the objects by at least one of the following steps:
• providing acoustical warnings on an aircraft intercom system;
• analyzing returns by subdividing the field of regard into a series of analysis windows, relating each of the returns to a particular one of the analysis windows from which the return came, performing a statistical analysis of the returns related to each of the analysis windows, and identifying returns that fall into a common range interval;
• transforming coordinates of objects measured relative to the aircraft to a horizon-stabilized, north-oriented coordinate system which is independent of the attitude of the aircraft;
• inserting the coordinates of identified objects into a data base so that the coordinates may be used for constructing a video display at a later time and updating the data base to correct for movements of the aircraft;
• and
• constructing a display of objects currently within the field of regard by adjusting the displayed position of the objects to compensate for avoidance maneuvers the pilot may execute;
• and thereafter,
• interfacing the video information to a video display system on the aircraft.

In a system for sensing objects along the flight path of an aircraft having a video display system and alerting a pilot of the aircraft to their presence, a method of alerting the pilot, comprising:

• detecting objects along the flight path of said aircraft to obtain range data and directional information on said objects to produce data representing the size and position of the objects relative to the aircraft, and updating the data as flight of the aircraft continues;
• producing a stream of video data from said object information and data corresponding to the range, azimuth and elevation of said objects,
• displaying a heading indicator on said display showing the intercept of the path of aircraft travel onto said video display,
• developing from the stream of data a line representing the lower limit of safe headings over the displayed images and for displaying said line on said video display, the area above said line representing a window of safety for the flight of said aircraft which may then be flown to keep the heading indicator above said line.

In an obstacle avoidance system for use on an aircraft for sensing objects along the flight path thereof and alerting the pilot to their presence, said aircraft having an avionics system for producing instrumentation data concerning the attitude and the velocity vectors of the aircraft and a video display for displaying information to the pilot, the method comprising:

• emitting a beam of laser energy pulses over a circular scan pattern repetitively moved about a field of regard along the flight path of said aircraft,
• receiving returns from objects within said field,
• processing the returns to produce data related to existence of objects on said flight path,
• analyzing said returns to identify wire-shaped objects bulky objects and calculating the range and direction information of said objects whenever found,
• producing directional information related to the instantaneous direction of the beam relative to the aircraft, processing the range data, directional information, and instrumentation data in order to produce a stream of data representing the range, azimuth and elevation of said objects,
• developing from the stream of data a line representing the lower limit of safe clearance headings,
• displaying a heading indicator on said display showing the intercept of the projected path of aircraft travel onto said video display,
• displaying said line on said video display, the area above said line representing a window of safety for the flight of said aircraft which may then be flown to keep said heading indicator above said line.