4.5 Scanning a Filter

The following procedure can be used to obtain a spectrum of a filter illuminated by white light (i.e. at nonthermal wavelengths). It is presumed that the servo system is locked.

1. Turn on the white light source and insert mirror 2.

2. Select the filter to be scanned.

3. Check the signal level on the detectors with the oscilloscope.

4. Run the ZPD task from the HP9000 workstation.

5. Fill out the SCANS menu on the HP9000 terminal. Only a small number of steps (e.g. 1024) is required.

6. Once the SCANS menu has been filled out, select Accept, and the scan will commence.

Note: not all filters can be scanned with the white light source. For broad band filters in the nonthermal infrared the detectors saturate, even with the light source set at minimum intensity, and in the thermal infrared the glass envelope of the white light source reduces the infrared radiation to impractical levels.