Chopper
The CH-60 optical chopper/shutter has modulation frequencies from dc to 50 Hz. The device has an aperture of 6.3 ¥ 11.4 mm. The small device offers jitter-free operation and high-frequency stability to 0.005%. Response time is 10 ms from an "open" to a "closed" position, or vice versa.
Electro-Optical Products Corp., Fresh Meadows, NY