Longitudinal KD* Ps are used in ground-based solar magnetographs to eliminate seeing effects by rapidly changing their retardation characteristics. Although one of the main applications for longitudinal KD*Ps has been their use as a variable retarder for "imaging" applications, an understanding of their limitations is important when developing scientific instruments that make very accurate polarization measurements. This paper will discuss some of the problems associated with the use of these devices in the Marshall Space Flight Center (MSFC) vector magnetograph. These problems include temperature, field of view errors, and electrical characteristics.
E. A. West,
"Using KD*P Modulators For Polarization Measurements Of The Sun", Proc. SPIE 1166, Polarization Considerations for Optical Systems II, (25 January 1990); doi: 10.1117/12.962914; https://doi.org/10.1117/12.962914