| 摘要 |
1,267,861. Diffraction grating systems. AGFA-GEVAERT A. G. March 3, 1969 [March 2, 1968], No.11236/69. Heading G2J. Images modulated in the form of a diffraction grating are photographically recorded on a carrier 11 and reproduced by illuminating the carrier 11 to give at least one non-zero order diffraction spectrum produced by the or each modulated diffraction grating. In one embodiment a photographic layer is exposed to an image of a grating with a degree of exposure sufficient to produce maximum density of image. The layer is then developed and bleached and re-exposed to the image to be recorded. Alternatively the layer can be exposed to an image of a grating at below the response threshold of the layer; the layer being exposed to the image before development. The grating may be produced by two interfacing light beams. Multiple images may be recorded by moving the grating between exposures, or by interposing a double-refracting crystal or bi-prism between the grating and the layer. In reconstruction a spatial filter 10, preferably located in the transform plane of a projection lens 9, blocks out zero order diffraction spectra. The required orders are projected on to an image plane 13. Where multiple images are recorded on carrier 11, each image modulated grating thereon has a unique azimuth angle and/or grating constant. If desired the record may be of a coloured image and comprise three layers, one for each primary colour. Thus the record will contain three gratings each modulated by a different colour separation image. In reproduction either the light beams produced by diffraction by the different gratings are passed through corresponding colour filters, or the components of the light beams that are not required are interrupted by a suitable spatial filter. |
