Method and apparatus for removing phase aberrations in windows using

Abstract

A method and apparatus are disclosed for correcting complex phase aberrations in a thick window in an airborne vehicle using the technique of phase conjunction. A conjugate element of the window is fabricated by machining. The conjugate element and an imaging lens are positioned behind the window such that the window is imaged onto the conjugate element. Phase aberrations produced when broadband radiation is passed through the window are removed when the wavefront passes through the imaging lens and conjugate element. In another embodiment, halogram is prepared of the wavefront passing through the window. The spatial phase information encoded in the hologram is read out by a phase measurement system and then fed into a computer where the conjugate wavefront is calculated. The conjugate wavefront is then written into a thin corrector plate of refractive material. The corrector plate with the conjugate wavefront imprinted thereon is then placed at the location where the hologram was initially formed. Phase aberrations produced when broadband radiation is passed through the window are removed when the wavefront passes through the plate. In another embodiment, the hologram is made of the conjugate element and imaging lens as positioned behind the window for phase aberration correction purposes instead of the window itself.