In a double-beam spectrophotometer using the optical null principle, a beam switch located behind the sample space makes the instrument sensitive to sample temperature. A double-chopping system utilizing two well-separated carriers was developed and applied to the far infrared instrument in order to eliminate the error due to sample radiation. The excellent performance demonstrates the usefulness of the double-modulation principle for far infrared instruments. Ease of change from the conventional single-chopping to double-chopping mode and simple construction are desirable features of this particular system.
© 1965 Optical Society of AmericaFull Article | PDF Article
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