System and method for binary focus in night vision devices

A night vision optical device comprising:

• an objective lens assembly positioned at a first or second focus position from an imaging device;
• and
• a binary focus controller, coupled to the objective lens assembly including:
• a line of sight (LOS) sensor coupled to the night vision optical device, configured to detect an orientation of the night vision optical device relative to a horizontal LOS, and
• a focus selector for selecting either the first or second focus position in response to the detected orientation of the night vision optical device,
• wherein the binary focus controller is configured to translate the objective lens assembly relative to the imaging device to either the first or second focus position responsive to the focus selector,
• the LOS sensor includes a pendulum mass coupled to the night vision optical device via a pendulum arm, the pendulum arm rotating with the pendulum mass responsive to the orientation of the night vision optical device, and
• the LOS sensor includes a linkage coupled to the pendulum arm and the focus selector includes:
• a first piston coupled to the linkage and positioned in a first pneumatic system at a first or second position based on a rotation of the pendulum mass, and
• the first or second position of the first piston, respectively, corresponds to the first or second focus position.

A method for controlling a focal position of an objective lens assembly positioned from an imaging device in a night vision optical device, the method comprising:

• detecting an orientation of the night vision optical device relative to a horizontal line of sight (LOS);
• selecting either a first or second focus position in response to the detected orientation of the night vision optical device;
• and
• translating the objective lens assembly relative to the imaging device to the selected focus position;
• wherein selecting the second focus position includes:
• determining a tilt angle of the night vision optical device in response to the detected orientation;
• selecting the first focus position when the tilt angle is less than or equal to a first predetermined threshold;
• selecting the second focus position when the tilt angle is greater than or equal to a second predetermined threshold, the second predetermined threshold larger than the first predetermined threshold;
• and
• maintaining a previously selected focus position when the tilt angle is greater than the first predetermined threshold and less than the second predetermined threshold.