![]() A description is given of the special industrial requirements for making high quality embossed patterns in this way on a large scale. A nickel master is made from the original photoresist by electroplating, and this master is then used to repeatedly emboss the pattern into long plastic sheets. Because the periodic arrays are required in large quantities, the patterns formed in photoresist must be replicated. The second and third processes produce surface depressions in the photoresist layer that occupy practically all of the available surface area. In the third process a square close packed hole pattern (egg-crate array) is formed using a single simultaneous four-beam exposure. In the second process a hexagonal close packed hole pattern (honeycomb array) is formed using a single simultaneous three-beam coherent exposure of the photoresist. Upon development an array of hills and valleys is formed, with the valleys corresponding to the holes and occupying about half of the available surface area. In the first process a square hole pattern is formed using two sequential two beam interference exposures in a thick layer of positive photoresist. A method is described for producing the array patterns using the technique of multiple beam interferometry applied to the already well known techniques of holographic grating formation. One use of such an array is the regular positioning of photosensitive elements, including, for example, photographic emulsion grains, into film systems of exceptionally low noise. In the photographic industry, two dimensional periodic arrays, or hole patterns, that have a periodicity on the order of one to several micrometers, can have many significant applications. This holographic grating is designated "Type V." Two interferometers capable of recording grating wavefront aberrations in the extreme UV and soft X-ray are proposed. An interferometric method of fabrication is also discussed, in which the recording wavelength is scaled-up into the far UV or even visible region of the spectrum. A concave varied line-space grating has been measured to achieve 70% of its theoretical efficiency in the extreme UV. ![]() Both straight-groove and concentric-groove patterns have been successfully fabricated with varied line spacings through mechanical ruling techniques. Ray traces of the concentric groove grating, the oriental fan grating and variations illustrate their potential for space astronomy and laboratory applications in the wavelength range of approximately λλ10-1000 Å. To achieve this characteristic, the groove spacings are varied in a continuous manner across a plano grating aperture. Recent work in the design of soft X-ray and extreme UV spectrographs has identified a new class of reflection gratings whose aberrations do not increase at grazing incidence.
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