| 摘要 |
1,179,212. Uses of photochromism. INTERNATIONAL BUSINESS MACHINES CORP. 31 May, 1968 [29 June, 1967], No. 26083/68. Heading C4S. [Also in Division G2] A method of manufacturing a spatial filter capable of producing a marker beam in its output when illuminated by a character beam comprises introducing the character into a beam of coherent radiation to produce a diffraction pattern which is recorded on a photochromic strip, and then introducing the marker, the character and the record of the diffraction pattern into the same or a substantially identical beam of radiation to produce an interference pattern and recording this pattern to produce the required filter. A point source 10 of light is collimated 12 to produce coherent parallel waves. These pass through a character plane 16 in which are mounted the character 24 and marker 26, in the form of transparencies, thence through a focusing lens 18 to an output plane 20 in which is located a photochromic strip 34, and behind that a strip 22 of photographic film. A shutter 30 is located between marker 26 and plane 20, and a shutter 32 between strips 34 and 22. As a first step shutters 30, 32 are closed and light is passed through character 24 only to provide a diffraction pattern recorded on photochromic strip 34. In a second step shutters 30, 32 are opened and photochromic strip 34 exposed to light from both character 24 and marker 26, and the film 22 to the resultant transmission of the doubly exposed strip 34 to record the interference pattern between character 24 and marker 26, and intiate exposure of character 24. The film 22 then becomes a halogram and forms the spatial filter such that on reconstituting by illuminating with a beam from the character an image of the marker will be produced. |
