| 摘要 |
PURPOSE:To prevent interference fringes recorded on a dry plate from fogging by reflecting part of two pieces of luminous flux for exposure to a mirror block which oscillates together with the dry plate and thus constituting an interference fringe monitoring system, and interrupting the exposure temporarily when harmful oscillation is detected. CONSTITUTION:Two pieces A and B of luminous flux which is made incident on the dry plate 1 to form interference fringes are reflected by mirrors 2a and 2b of the mirror block 2 fitted to the dry plate 1 during exposure to obtain pieces Aa and Ba of luminous flux, which is made incident on an interference fringe monitor 3 to form interference fringes. The grating intervals of the formed interference fringes are sufficiently large and the fringes are observed easily even when projected on, for example, the screen of a cathode-ray tube. Then, the mirror block 2 even when there are oscillations oscillate together with the dry plate 1, so oscillations of the interference fringes on the surface of the dry plate 1 are observed while magnified through th interference fringe monitor 3. If harmful oscillations are found by said observation, the exposure is interrupted by closing the shutter of an optical system for hologram formation immediately, and the exposure is restarted a specific time late and carried out until the integral time value of the exposure attains to a specific value to suppress the occurrence of fogging, thereby obtaining a hologram having invariably high diffraction efficiency. |
