Performance Test Of The Compound Diffractive Telescope

Today advances in small satellites put forward higher requirements to space optical telescope, to solve the mass-and-launchability problems, a membrane mirror or a diffractive optical element is used to form an ultra-lightweight telescope, however, both of them have problems: either the surface precision is too high to be fabricated or the field of view (FOV) is restricted by the weight of the eyepiece.The compound diffractive telescope is a new kind of space telescope, which combines the diffractive optics with the structure of compound eyes, so the new telescope is lighter in weight, wider in FOV, lower in cost and lower in sensitivity to manufacturing tolerance. For such set of the telescope which is comprised of one 50mm aperture of refractive-diffractive hybrid lens and twenty-one 8mm aperture of eyepieces, the following works about the thesis is mainly about:1: The optical parameters about the compound diffractive telescope is optimized with Zemax program, the FOV for each eyepiece is about 0.2°, the modulation transfer function (MTF) value is higher than 0.8 at 50lp/mm for the central channel, while the MTF value is about 0.7 at 50lp/mm for marginal channels.2: As the diffraction efficiency of the diffractive optics will influence the imaging quality of the compound diffractive telescope, we analyzed the MTF curves and the energy distribution on the detector separately with mathematical program Matlab and Advanced System Analysis Program (ASAP), it is found that the adverse influence to the system is small with a 16 steps'binary surface. An optimized mechanical structure is proposed for the eyepiece.3: Two refractive-diffractive hybrid lenses and ten eyepieces have been fabricated, the star image and resolution tests to the system have been done with a 1600mm collimator, one perfect Airy disk is taken form the central channel. The compound diffractive telescope has been aligned, a series of pictures are taken from distant and infinity objects separately, finally the result of the imaging experiment is analyzed particularly.4: For high precision tests of the wavefront and the focal length of long focal length,large F number lens at the same time, two kinds of method is proposed: the Computer-Generated Holograms (CGH) method and the concave spherical mirror method. The optical surface test formula and the focal length test formula for this kind of lens are derived, the particular error analysis for these methods are done separately, at last, a lens with an aperture of 50mm and f '= 2450mm is tested with the concave spherical mirror method.