The paper describes a method for preparing plastic replicas of any existing mirror without using a negative glass master. In this two-step process a SiO-coated epoxy negative master is first prepared from the original mirror. This negative master is then used to produce plastic replicas which duplicate the original mirror. Epon 828 resin and Curing Agent Cl(meta phenylene diamine) were used to prepare the backing of the negative master and the final mirrors. A great number of f/1to f/2 paraboloidal replicas was prepared by this method and compared optically with the original mirrors. The accuracy of the mirrors was tested by focusing incident collimated light on small pinhole apertures of various sizes and measuring the ratio of the light transmitted through the apertures to the total amount of light in the focal plane. With the mirrors used for reproduction, it was found that the replicas were, within the range tested (down to 0.18-mm aperture size), as accurate as the original glass mirrors. Plastic replica mirrors can be cleaned repeatedly without damage and have been transferred directly from dry ice to boiling water without breaking or changing their appearance.
© 1959 Optical Society of AmericaFull Article | PDF Article
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