| 摘要 |
<p>An apparatus for sensing data from a remote optical sensor (16) has its frequency stabilised by balancing the outputs of narrow band filter (28, 30) , spaced about a desired frequency (36) positioned at about the 3db down point s (40) of a broad band light source (10) using voltage control, current contro l or temperature control to vary the frequency of the wide band light source (10). Difference between the outputs through the two narrow band filters (28 , 30) can be used to drive an amplifier (48) to correct the frequency of the broad band light source. The outputs through the two narrow band filters (28 , 30) can be converted (52) to binary numbers and fed to a microprocessor (56) which is used, via analog conversion (60), to drive the amplifier (48). The broad band light source (10) can be pulse modulated (68) to provide temporal ly separate light pulses (92, 94) through each of the narrow band filters (28, 30), measured at separate times. The corrective output to the amplifier (48) can be governed by a ratio between the outputs through the narrow band filte rs (28, 30) rather than by a difference there between.</p> |
