High-performance infrared filters for the HIRDLS 21-channel focal plane detector array

  • Roger Hunneman, John J. Barnett, Gary J. Hawkins
  • September 1994, SPIE
  • DOI: 10.1117/12.188110

Infrared filters for Earth observation

What is it about?

The High Resolution Dynamics Limb Sounder is described, with particular reference to the atmospheric measurements to be made and the rationale behind the measurement strategy. The demands this strategy places on the filters to be used in the instrument and the designs to which this leads to are described. A second set of filters at an intermediate image plane to reduce "Ghost Imaging" is discussed together with their required spectral properties.

Why is it important?

A method of combining the spectral characteristics of the primary and secondary filters in each channel are combined together with the spectral response of the detectors and other optical elements to obtain the system spectral response weighted appropriately for the Planck function and atmospheric limb absorption. This method is used to demonstrate whether the out-of band spectral blocking requirement for a channel is being met and an example calculation is demonstrated showing how the blocking is built up for a representative channel.


Dr Gary J Hawkins
University of Reading

The spectral requirements of the HIRDLS instrument have been discussed and described. It has been shown that the instrument spectral blocking requirement can be met using a combination of two interference filters and the materials present in the optical train. A method of verifying that the necessary Margin Ratios have been achieved is presented, together with an example of its application to a typical spectral channel.

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The following have contributed to this page: Dr Gary J Hawkins