Production of moldings with longitudinal grooves and ridges comprises heating preform and stretching it, radiation being used whose power is such that at most half of it is absorbed in passing through preform

摘要

Production of moldings with longitudinal grooves and ridges comprises heating a preform (1) with corresponding grooves and ridges (3 - 10) and stretching it to reduce its cross-section to the required value. Heating is carried out using radiation whose power is such that at most half of it is completely absorbed in passing once through the preform. Independent claims are included for: (a) moldings produced by the process; (b) spacers consisting of the moldings; (c) transmission or reflection grids containing the moldings; (d) grids with spread Bragg reflection containing the moldings; (e) spectrometers containing the grids; (f) communications devices containing the moldings; (g) apparatus for carrying out the production method comprising a infra red heater for heating the preform, a holder for one end of the preform and a device for stretching it; and (h) a production method as above in which the maximum temperature difference across the cross-section of the preform is less than 0.5[deg]C.