离轴抛物镜 off-axis parabolic mirror 离轴抛物面反射镜 minimize system sizes minimize system weight both "wedged" and equi-thick mirrors are available minimize system cost target simulators collimators mtf measuring systems and other optics test devices spectroscopic and ftir systems radiometers beam expanders laser divergence measuring systems to fully describe oap one has to specify 5 parameters: 1.parent focal length pfl (or slant focal length sfl) 2.zonal radius zr (or off-axis distance oad) 3.ca (clear aperture) 4.sa (surface accuracy) 5.sq (surface quality) off-axis parabolic mirror draft typical interferometer graph of oap mirror surface error profile reconstruction typical reflection spectrum for protected aluminum (al + sio2) coating