09 Apr 2009 Scitec Instruments offers an optical chopper that uses 200 mm diameter discs, which allows modulation of larger diameter beams. Scitec Instruments' Model 340CD Optical Chopper enables optical beams of up to 78 mm diameter to be modulated at frequencies of up to 220 Hz.
Two discs are available. A two slot disc provides chopping frequencies from 5 to 110 Hz and a four slot disc provides chopping frequencies from 10 Hz to 220 Hz.
The chopper system consists of a Control Unit with frequency display , a Chopper Head, an Interconnecting Cable and a choice of either a 2 slot or 4 slot 200 mm diameter disc. | 
