REAL-time holographic compesniation of large optics for deployment is space

摘要

Large depolyable space-based optical systems will kilely require complex structure position controls in conjuction with an adaptive optic to maintain optical tolerances necessary for near diffraction-limited performance. A real-time holographic (RTH) compensation system can treatly educe the requirements and complexity of the position control system and enable the use of novel ir imperfect optical components for large mirror surfaces. A hologram of the distorted primary is recorded with a local beacon at 53 nm (approx 100 nJ/exposure) on an optical adressed spatial light modulator and transferred as a phase grating to a ferroelectric liquid crystal layer. The hologram is played back with target light containing the same optical distortion. A corrected image is obtained in the conjugate diffracted order where the phase of the optical distortion is subracted from the distorted image. We report recent test reults and analysis of a RTH-compensated deformed mirros of 0.75 m diameter. The short expousre hologram is recorded at video frequencies (30 Hz) at bandwidths up to 5 kHz. Correction for tens of waves of static and hyamic optical distortilns including mechanical and thermal warp, mechanical vibration, and air turbulence are shown for monochromatic (532 nm) and broadband (532 +- 40 nm) illuminated targets. We also report on the generation of blazed gratings in electrically addressed spatial light modulators to achieve gratly enhanced diffraction efficiies and to perform beam steering.