Patent ID: 7545509

Claim:
An apparatus for determining and implementing a control action associated with a characteristic of paper in a manufacturing process, the apparatus comprising: a first coherent electromagnetic energy source, the first coherent electromagnetic energy source producing a generator beam of coherent electromagnetic energy, the generator beam of coherent electromagnetic energy impinging the paper and generating a sonic energy signal about the paper; a second coherent electromagnetic energy source, the second coherent electromagnetic energy source producing a measuring beam of coherent electromagnetic energy, wherein the measuring beam of coherent electromagnetic energy is coaxially applied to the paper with the generator beam of coherent electromagnetic energy, the measuring beam of coherent electromagnetic energy impinging the paper, the measuring beam of coherent electromagnetic energy reflecting from the paper as a scattered electromagnetic energy, the scattered electromagnetic energy having a modulation associated with the sonic energy signal; an interferometer, the interferometer collecting part of the scattered electromagnetic energy and deriving a signal indicative of the sonic energy signal from the scattered electromagnetic energy; an interpreter, the interpreter determining the characteristic associated with the paper from the signal indicative of the sonic energy signal; a controller, the controller determining a control action associated with the characteristic associated with the paper; and an optical amplifier operable to amplify the scattered electromagnetic energy prior to the interferometer.