| 摘要 |
Device, method, and system for recording diffractive high resolution text, pictorial, and/or other graphical information is provided which is particularly suited to recording information that would be difficult to reproduce by typical counterfeiting methods. The information recorded may be used to authenticate the recorded item, or indirectly, an item to which the recording is attached. Such items may include legal, financial and commercial instruments, credit cards, and packaging for such items as software, art, and other items where forgery of the item may be a concern. In one embodiment of the invention light is selectively passed by a shutter, and a spatial filter then cleans the beam to remove undesirable frequency components. A liquid crystal display (LCD) dynamically receives a data stream from a computer where each of the displayed data values presents an optical characteristic (for example density, phase, or polarization) to the filtered beam and causes diffraction into a plurality of diffracted beams, the character of which is dependent on the data displayed. A mask selectively passes only predetermined ones of the beams so that only frequency components that will generate the desired optical interference fringes are allowed to pass. Additional optical components receive the passed beams and redirect them to overlap at an output plane to form interference fringes. These interference fringes can have a very high spatial frequency so that extremely fine lines or small objects, including text and graphics, can be recorded.
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