自适应光学波前传感技术..

哈 特 曼 夏 克
Hartmann wavefront sensor
Hartmann wavefront sensing technique. A Hartmann sensor is composed of an array of lenses for wavefront division and typically a CCD array with multiple pixels used for spot position (wavefront tilt) determination.
哈 特 曼 夏 克
History
Shack placed lenses in the holes, which increased the light-gathering efficiency of the mask and, with the spots focused, reduced the disturbing diffraction effects of the holes. A lens array for this purpose was first manufactured in 1971.Members of the astronomy community began to use this sensor in the late 1970s for testing of large telescope optics.Some astronomers use the term Hartmann–Shack (or Shack–Hartmann) wavefront sensor, but many shorten it to simply Hartmann sensor. 哈 特 曼 夏 克
工 作 成 绩
Hartmann test
One method for testing a lens or mirror employs an opaque mask with holes placed behind the optical element under test.Each of the holes acts as an aperture, and since the light passing through the lens is converging, the image produced is an array of spots.With proper calibration, the position of the spots is a direct indication of the local wavefront tilt at each hole, and thus is a description of the lens quality.This test is called the Hartmann test.
自适应光学波前传感技术
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哈特曼夏克波前传感
Evolution of the Hartmann test – standard devices for measuring wavefrxtended object
If that source is an extended object, the shape of the object is convolved with the subaperture diffraction pattern on the quadcell.Intensity variation can seriously degrade the measurement accuracy of the centroid.To remove the effects of extended objects resolved by the subaperture, an optical correlation can be used. Von der Luhe suggested the use of an addressable optical mask, whose transmission is derived from the image of the reference scene.The Hartmann detector array records a cross-correlation of the mask and the scene in each subaperture.Even if the object remains unresolved, the problems associated with subaperture higher-order aberrations will distort the pattern on the quadcell and decrease tilt-measurement accuracy.
Hartmann wavefront sensor
The Hartmann wavefront sensor is shown in below figure .The wavefront is divided by a mask, as in the classical test, an array of gratings, or an array of transmissive lenses.Each of the beams in the subapertures is focused onto a detector.To detect the position of the spot, various forms of modulation, detector geometry, and electrooptical processing are used. For atmospheric turbulence compensation, the local r0 measured accurately in each wavefront tilt must be subaperture of size .To do this, the subaperture must be large enoughr0 to resolve the isoplanatic patch.During high turbulence, is small and anisoplanatism degrades the process.Hardy discusses details of this large-versussmall subaperture trade for various optical and atmospheric