Schlumberger Technology Corporation

Timothy Jeffreys

Arthur H Hartog

Maxwell Richard Hadley

Yuehua Chen

James McInnes

An apparatus for sensing data from a remote optical sensorhas its frequency stabilised by balancing the outputs of narrow band filter, spaced about a desired frequencypositioned at about the 3 db down pointsof a broad band light sourceusing voltage control, current control or temperature control to vary the frequency of the wide band light source. Difference between the outputs through the two narrow band filterscan be used to drive an amplifierto correct the frequency of the broad band light source. The outputs through the two narrow band filterscan be convertedto binary numbers and fed to a microprocessorwhich is used, via analog conversion, to drive the amplifier. The broad band light sourcecan be pulse modulatedto provide temporally separate light pulsesthrough each of the narrow band filtersmeasured at separate times. The corrective output to the amplifiercan be governed by a ratio between the outputs through the narrow band filtersrather than by a difference there between.

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Winchester, United Kingdom

Timothy Jeffreys