PARTICULATE MATTER DETECTION METHOD

摘要

Use a ceramic honeycomb filter (11) wherein collecting holes (11d) form a lattice, to detect particulate matter collected in the filter (11). Transmit an electromagnetic wave (D) toward the filter in the plane perpendicular to the longitudinal direction (P) of the collecting holes (11d), receive the electromagnetic wave (E) which has penetrated the filter, and detect the particulate matter collected in the filter on the basis of the reception intensity of the electromagnetic magnetic wave. The frequency of the electromagnetic wave is at least 0.294 c/a but not exceeding 1 c/a (a being the lattice interval of the collecting holes, and c being the speed of light); and the titling angle (?) of the electromagnetic wave relative to the lattice is altered by irradiating an electromagnetic wave on a filter which has not collected any particulate matter, and altering the tilting angle so that the reception intensity of the electromagnetic wave increases.