| 摘要 |
<p>A method for producing an optical element (17) comprising an optical surface the contours of which define a waveform the amplitude of which as measured with respect to a datum surface is related to the amplitude of an interference pattern generated at the datum surface by interference between two coherent beams of radiation. The beams are generated in and transmitted to the datum surface through a particle free vacuum. The axes of the beams are mutually inclined, and each of the beams is of uniform intensity across the beam wavefront. At least one of the beams diverges from a single point or converges towards a single point.</p> |
