Establishing and maintaining focus in segmented-optic telescopes
AssigneeVenture Ad Astra, LLC
InventorGeoffrey B. Rhoads
Life of this patent
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Abstract
A multi-aperture interferometric optical system collects light propagating from a source of light and develops overlapping diffraction patterns on an optical detector that produces output signals for processing to automatically focus the optical system and form an image corresponding to the diffraction patterns. A preferred embodiment of the invention is a large aperture orbiting, earth-watching ring interferometric optical system configured such that there is no macro-structure pointing. Four mirror-ring structures direct incoming light to a multi-spectral primary optical detector that acquires light-pattern information to focus the optical system and derive an image.
Claims27
A multi-aperture interferometric optical system formed of multiple mirror segment trains cooperating to focus incident electromagnetic radiation at a focal plane, the optical system comprising:
- a set of spaced-apart segment trains arranged around a region on a focal plane and configured to generate a diffraction pattern at the focal plane, each segment train comprising a set of mirrors configured to reflect incident electromagnetic radiation toward the focal plane;
- a detector positioned at the focal plane and configured to generate data for focusing the optical system and forming an image from the diffraction pattern;
- multiple mirror actuators associated with the segment-train mirrors, the multiple mirror actuators configured to respond to actuator commands by moving respective segment-train mirror positions;
- and
- a controller configured to, based on the data from the detector, estimate a bias representing a misalignment of the optical system, and, based on the estimated bias, generate actuator commands for controlling the multiple mirror actuators to establish and maintain focus of the optical system.
A method of establishing and maintaining focus of a multi-aperture interferometric optical system formed of multiple mirror segment trains cooperating to focus electromagnetic radiation on a detector positioned at a focal plane, the method comprising:
- calibrating each segment train such that images formed on the detector by each segment train are substantially coincident and the segment trains are within operational coherent range of one another, thereby establishing focus of the optical system;
- and
- maintaining focus of the optical system by imparting incremental modulations to each segment train, estimating a wavefront error corresponding to each segment train over multiple data frames based on differences between spatial-spectral transforms of a set of sequential data frames corresponding to images formed on the detector by the respective segment train in response to the incremental modulations, and applying reactive modulation increments to at least one segment train based on the respective estimated wavefront error.
A method of generating actuation commands for establishing focus of a segmented optical system formed of multiple mirror segments cooperating to focus electromagnetic radiation on a detector positioned at a focal plane, the method comprising:
- shifting an image of a scene in first and second orthogonal directions on the detector by adjusting a tip and tilt position, respectively, of at least one mirror in each of the segments;
- for each adjusted mirror, determining specific rotations of phase vectors in first and second orthogonal frequency bands resulting from the respective shift in the first and second orthogonal directions by comparing an image of the scene after the respective shifts in the first and second orthogonal directions to an unshifted image of the scene;
- for each adjusted mirror, calculating a distance between tip and tilt values of the adjusted mirror and average tip and tilt values of the corresponding mirrors in the other segments based on the determined specific rotations of phase vectors in the first and second orthogonal frequency bands, respectively, thereby yielding calculated distances for each of the segments;
- and
- generating actuator commands for adjusting a tip position, a tilt position, or both, of at least one mirror based on the calculated distances.
A method of generating actuation commands for maintaining focus of a segmented optical system formed of multiple mirror segments cooperating to focus electromagnetic radiation on a detector positioned at a focal plane, the method comprising:
- generating actuator commands for incrementally modulating a tip component, a tilt component, a piston component, or a combination thereof, of a mirror in each segment;
- for each incrementally modulated mirror, estimating a wavefront error corresponding to the tip component, the tilt component, and the piston component of the mirror over multiple data frames based on a response of the mirror to the incremental modulation;
- and
- generating actuation commands for applying reactive modulation increments to the tip component, the tilt component, the piston component, or a combination thereof, of at least one mirror based on the respective estimated wavefront error.
Dependencies are inferred from the claim text.