CONICA-SAR

Optical design of the Superachromatic Retarder

A superachromatic l/2 retarder similar to the B Halle standard device RSU2.2.25 has been integrated into CONICA (Apr. 2004). The device has been mounted in front of the CONICA focal plane:

We have replaced the TADC device by the retarder plate, thus, no additional rotation mechanism was required. The Mechanical and SW-structure of the TADC device can be used to realize this retarder facility. Only small nomenclature modifications are required.

Fig. 10: Wavelength retardation versus wavelength for a Quartz/MgF2 Superachromatic retarder

To dismount both TADC plates, the adapter has to be de-attached from the Nasmyth focus.

The Superachromatic Retarder will be mounted into the TADC-device that is about 12cm pre-focal within the collimated beam. This produces a slightly wavelength depending focus shift due to a total MgF2 thickness of 3.43mm and a Quartz plate thickness of 4.35mm. The resulting focal shift is shown in the following Fig.: 11

Fig. 11: Focus shift versus wavelength of the proposed               superachromatic retarder in front of CONICA.

The free aperture of the new retarder is 45 mm. Given a distance of 50 mm in front of the focal plane, the effective usable FOV without vignetting is 44 mm, thus, quite exactly the diagonal value of Camera 54 mas/pixel. All cameras can be used in combination with the proposed retarder without any significant vignetting.

Responsible: Rainer Lenzen
Last updated: May 11, 2004