The New Focus 3501 Optical Chopper Controller is a precision instrument that generates stable chopping frequencies for interrupting light paths in experimental setups. It employs a crystal-controlled frequency synthesizer to achieve frequencies from 4 Hz to 6.4 kHz with minimal jitter and drift. Active motor speed stabilization via photo-sensor feedback ensures long-term frequency stability and reduced phase noise across single and dual beam configurations.
Technical Specifications
• Chopping Frequency Range: 4 Hz to 6.4 kHz
• Frequency Control: Crystal-controlled frequency synthesizer
• Harmonic Chopping: 2 to 15× selectable
• Subharmonic Chopping: 1/2 to 1/15× selectable
• Phase Control: −180° to +179° with respect to reference frequency
• Operating Modes: H/S (Harmonic/Subharmonic), +/−, NORMAL
• Setup Memory: Nine user-defined setups with power-loss retention
– Key Features
• Dual TTL output signals (OUT1, OUT2) with mode-dependent frequency outputs
• OUT1 generates frequencies according to operating mode: H/S Mode outputs [H/S]·Fsync; +/− Mode outputs Fouter − Finner; NORMAL Mode outputs 5·Fouter
• OUT2 generates complementary outputs: H/S Mode outputs [H/(7·S)]·Fsync; +/− Mode outputs Fouter + Finner; NORMAL Mode outputs Finner
• External synchronization via Sync Input for locking to reference sources
• Synthesizer reference output for downstream applications
• IEEE-488 interface for remote instrument control and automation
• Motor connector accepts six-conductor reverse RJ11 IDC telephone cable
• Motorola connectors on rear panel
– Typical Applications
Optical chopping for lock-in amplifier systems, beam modulation in spectroscopy, dual-beam interference experiments, and phase-sensitive detection requiring precise frequency and phase control.
– Compatibility & Integration
Connects to New Focus chopper heads via dedicated motor connector. Optional Model 3510 Rack Mount Kit enables standard 19-inch rack integration. IEEE-488 compatibility allows integration into automated measurement systems and remote laboratory control architectures.
