| 摘要 |
An apparatus 10 and method for the recording and readout of multiple exposure holograms. For recording, the plane of polarization of the multiple pulsed linearly polarized laser beam 14 from source 12 is rotated by half-wave plate 26. Polarizing beam splitter 20 then divides the beam 14 into a test beam 24 and a recording reference beam 22. The test beam 24 is directed through a quarter-wave plate 28, through a test medium in chamber 34, reflected from mirror 36, back to beam splitter 20 and finally to film plate 37. On a first pulse, a first recording reference beam 22, 22' is directed through pockel cell 38, is reflected by beam splitter 40, through half-wave plate 76, off of mirror 42 and finally to film plate 37 to form a first hologram. On a second pulse a second recording reference beam 22, 22'' is transmitted through beam splitter 40, reflected off mirror 48 and 50 and through half-wave plate 46, and finally directed toward film plate 37 forming a second hologram. For readout, a continuous wave readout laser beam 54 directs beam 56 through a half-wave plate 62 and then off mirror 55 toward beam splitter 60. The resulting readout reference beams 56, 58 are then frequency modulated by Bragg cells 64, 66 recombined at beam splitter 72, redivided by beam splitter 40 and directed along the same paths as the recording reference beams 22', 22''. Half-wave plates 46 and 76 adjust the readout reference beams to have the same plane of polarization as each other thereby producing a frequency modulated interference pattern on an interference plane. The optical path differences between the recorded wavefronts at a reference location in the interference plane and another spatial located in the interference plane may then be measured.
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