| 摘要 |
A thermoplastic plate, for example one of polypropylene or nylon, fabricated so it has an open-cell structure, has a radiation transparent cover sheet applied to one face thereof. The cover sheet has an energy absorbing coating (e.g. of carbon and nitrocellulose) in intimate contact with the plate. A modulated laser beam is then transmitted through said cover sheet to selectively transfer some of the energy absorbing material to the plate according to the configuration required to define the areas of relief desired in the plate. The cover sheet is then removed except for the portion of the energy absorbing coating transferred to the plate. The entire surface of the plate is then exposed to infra-red rays. The portions of said surface to which energy absorbing material was transferred are elevated in temperature, by the absorbed infra-red energy, to the point that the structure beneath the transferred material collapses, thus causing those portions to sink to a plane below the plane of the other portions of the plate. Additional infra-red heating steps may be performed to produce further collapse of said portions of the surface, as hereinafter more fully explained.
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