The Hinds Instruments PEM-200 is a fully digital controller for photoelastic modulators, replacing earlier analog designs with microprocessor-based drive electronics. It precisely regulates transducer vibration amplitude to control the peak retardation of the optical element, enabling accurate polarization modulation for spectroscopy, ellipsometry, and circular dichroism measurements.

What advantages does digital control offer over previous analog designs?

The digital architecture maintains a duty cycle of 50 percent with a deviation of only plus or minus 0.001 percent at both fundamental and second harmonic frequencies. This level of precision was unattainable with analog phase-locked loops, which drifted with temperature and component aging. The PEM-200 also auto-detects the connected optical head and configures drive parameters automatically, eliminating the manual tuning procedures required by earlier controllers.

What optical head compatibility does the PEM-200 support?

The controller is backward-compatible with all existing Hinds PEM optical heads when used with dual SMA coaxial cables. Supported optical materials include fused silica (170 nm to 2.6 μm), Infrasil (200 nm to 3.5 μm), and zinc selenide (2 μm to 18 μm), with nominal modulation frequencies from 37 kHz to 84 kHz depending on the head model and aperture size.