Apparatus and process for measuring physical parameters of sheet material

An apparatus for measuring physical parameters of sheet material by directing electromagnetic radiation from a source to the material and electronically processing detector responses associated with selected bands of radiation which passes through or otherwise interacts with the material, comprising:

• (a) first means for detecting a relatively broad band of radiation emitted from the source;
• (b) second means for detecting at least two relatively narrow bands of radiation emitted from the source;
• and
• (c) means for conditioning detector responses from the second means in accordance with a detector response from the first means to produce at least two conditioned responses.

A process for measuring physical parameters of sheet material by directing electromagnetic radiation from a source to the material and electronically processing infrared detector responses associated with selected bands of infrared radiation which passes through or otherwise interacts with the material, comprising the steps of:

• (a) filtering the electromagnetic radiation to pass a relatively broad band of radiation;
• (b) detecting the radiation passed in the filtering step to produce a phase-reference detector response;
• (c) simultaneously filtering the electromagnetic raditation to simultaneously pass at least two relatively narrow bands of radiation;
• (d) separately detecting the different bands of radiation passed in the simultaneous filtering step to produce at least two infrared detector responses;
• and
• (e) conditioning the infrared detector responses in accordance with the phase-reference detector response to produce at least two conditioned responses.