Optics: measuring and testing – By dispersed light spectroscopy – Utilizing a spectrometer
Patent
1981-06-01
1983-11-08
Arnold, Bruce Y.
Optics: measuring and testing
By dispersed light spectroscopy
Utilizing a spectrometer
G01B 902
Patent
active
044139098
ABSTRACT:
Wavefronts defined by square subapertures (13, 14, 15) are focussed into spots of light on a grating (17) having two intersecting sets of lines, which diffract each wavefront into two coinciding zeroth order components and four spaced-apart first order components. For each wavefront, the various orders of diffraction components are collimated to form corresponding images of the subaperture defining the wavefront. Quadrant detectors (23, 24, 25) are located so that zeroth order image (301) of subaperture (13) fills all quadrants of detector (23), zeroth order image (401) of subaperture (14) fills all quadrants of detector (24), and zeroth order image (501) of subaperture (15) fills all quadrants of detector (25). The four first order images of each subaperture are spaced apart from each other, but overlap and interfere with four different portions of the zeroth order image: i.e., first order images (321, 322, 323, 324) overlap zeroth order image (301) to produce interference patterns ( 351, 352, 353, 354); first order images (421, 422, 423, 424 ) overlap zeroth order image (401) to produce interference patterns (451, 452, 453, 454); and first order images (521, 522, 523, 524) overlap zeroth order image (501) to produce interference patterns (551, 552, 553, 554). Each interference pattern on each detector appears on a different quadrant of that detector. Relative motion between the diffraction lines on grating (17) and the spots of light focussed onto grating (17) is provided in order to cause periodic temporal fluctuations in the intensities of the four interference patterns appearing on each of the detectors (23, 24, 25). Any phase difference occuring between the intensity fluctuations of interference patterns on corresponding quadrants of different detectors (23, 24, 25) is a measure of the relative positions of the spots of light with respect to the sets of lines on grating (17). The relative positions of the different spots of light on the grating (17) provide an indication of the relative tilts of corresponding subaperture wavefronts with respect to each other or with respect to a reference tilt.
REFERENCES:
patent: 3829219 (1974-08-01), Wyant
patent: 4239392 (1980-12-01), Pohle
patent: 4330211 (1982-05-01), Peterson et al.
Arnold Bruce Y.
Lockheed Missiles & Space Co., Inc.
Morrissey John J.
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