Applying normalized processing to each atom: $d\u2192(r\u2032,\omega ,\theta )=d\u2192(r\u2032,\omega ,\theta )/\Vert d\u2192(r\u2032,\omega ,\theta )\Vert 2$, then the atom set can be represented as Display Formula
$D=[d\u2192(1,1,1),\u2026,d\u2192(1,1,N\theta ),\u2009d\u2192(1,2,1),\u2026,d\u2192(1,2,N\theta ),\u2026,d\u2192(1,N\omega ,N\theta ),d\u2192(2,1,1),\u2026,d\u2192(2,N\omega ,N\theta ),\u2026,d\u2192(Nr\u2032,N\omega ,N\theta )]M\xd7Nr\u2032N\omega N\theta .$(7)