 The close examination of DFT and DHT, shows that the 3-D DHT of ' of a spatially-planar signal ' is zero outside the straight line ' passing through the origin of 3-D DHT ' space.Therefore, formula_448 formula_458 Zformula_459 formula_135/formula_440=formula_136/formula_442}, where Z refer to the set of integers.All the LDE's that correspond to 2-tuples {formula_135,formula_136}, that lie outside the fan shaped projection of the thin pyramidal passband on the formula_135-formula_136 plane have to be omitted.