| 摘要 |
1317592 Holography K BIEDERMANN 18 May 1970 [17 May 1969] 23864/70 Heading G2J [Also in Division G1] In holographic apparatus wherein a hologram is recorded by exposing a medium 13 a laser produces a beam which enters an interferometer which measures the mechanical stability of the apparatus and operates a shutter to interrupt exposure when the vibrations exceed a desired value. The interferometric measuring beam strikes a beam splitter 17 giving one portion which is reflected back on itself by a mirror 18. The other portion follows a path via a mirror 5, mirror 19 rigidly attached to a lens in the object beam path, mirror 10 in the reference beam path.and a mirror 20 from which it is reflected back along the path to beam splitters 17. There it interferes with the beam portion from mirror 18. This interfering beam is again split at 21 half passing to each of two non-linear photo-resistors 22, 23, in front of one of which 23 is a diffuser 24. These measure any change in the fringe pattern cammed by vibrations of the apparatus. The output from a measuring device 26 is connected to a shutter 14 or 14'. In one embodiment the photo-resistors 22, 23 are replaced by a single photo-electric transducer located behind an aperture in a screen. The interferometer is so adjusted that the fringe cycle is four times the aperture width. In a further embodiment use is made of the principle of a Mach Zender interferometer, Fig. 3. Part of the object beam is reflected from a mirror 33 located on the object holder, and this beam then strikes a beam divider 32, located in the bisector plane for the object and reference beam at hologram recording plate 13, where it interferes with a portion of the reference beam. The resultant fringes are measured by a transducer 30 located behind an apertured screen 28. Any resultant adverse signal operates shutters 36, 37. If desired a transparency, having the same fringe density and orientation as the interference fringes, may be located in front of aperture 29. The apparatus may be a holographic camera. |
