The standard surface can be used to make an almost perfect axicon. If (1+k)C^2R^21, the standard surface reduces to Z=r/sqrt(-1-k) or z=rtan(alpha) , where tan(alpha) = 1/sqrt(-1-k) ,
and alpha is the axicon angle, measured from the XY plane to the axicon surface. To create an axicon, calculate the conic constant value (k) from the angle (alpha ) desired, and use any small value for the radius of curvature. The resulting value of k must be negative. The exact value of the radius or curvature is not important, as long as it is roughly three or more orders of magnitude smaller than the radial aperture of the axicon. The axicon is not perfect in the sense that there is no cusp at the origin; the region around the surface vertex will be rounded off over a size given approximately by the radius value. This is actually a desirable property for ray tracing, as the surface is everywhere smooth.
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发表于 2006-11-30 18:19:00
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