Enclosed Head Optical Choppers

Enclosed Head Optical Choppers

The 75160NF enclosed optical chopper is used to introduces a periodic interruption of the light path in an optical experiment, resulting in an amplitude modulation. This is useful for many small optical signal detection schemes. The chopping frequency is phase-locked to its own internal frequency synthesizer, providing rock-solid stability and flexibility.

Complete Chopper System for Spectoscopy Applications

Block diagram for Chopper ManualFunctional block diagram for Model 75160NF Optical Chopper System

The 75160NF comes complete four chopper wheels, an enclosed chopper head with Oriel mounting flange, and a chopper controller with USB 2.0 interface. All it require to run is connect power cable and its ready for chopping action.

Stable and Reliable Phase Locking

For stable chopping with minimum jitter and drift, the chopper head uses precision photo-etched wheels mounted on a high-quality DC motor. In addition, the chopper controller has its own internal crystal-controlled frequency synthesizer and phase-locked loop for precisely locking the chopping frequency. A photo-interrupter on the chopper head monitors the chopping frequency, and the chopper controller actively stabilizes the motor speed to ensure stable chopping with a minimum of frequency drift.

Enclosed Chopper Head

75150-1050-366Dimensions of Oriel Optical Chopper Head

The controller drives the chopper head containing a multi-aperture wheel to modulate the light. The chopper head includes Oriel 1.5-inch series flanges, which couple to a wide variety of Oriel instruments. Chopper wheels are easily interchangeable. The enclosed chopper head design prevents detector saturation from unchopped background light and prevents scattering. When chopping lasers or UV beam, you can reduce potential hazards by enclosing the beam path.

Four Broadband Absorber Coated Chopper Wheels Included

BPT-pg6-97bMaximum beam diameter is dependent on wheel aperture size.

The 75160NF comes with four chopper wheels. Oriel chopper wheels are precision etched, and coated with a broadband absorber to minimize retroreflections. The chopping rate may be set from 4 Hz to 2.00 kHz depend on the chopper wheel.

Advanced Optical Chopper Controller


The front panel display of the controller allows monitoring of the chopping frequency, as well as a number of other operating parameters. Easy-to-use cursor keys provide easy adjustment of operating parameters. The chopping rate may be set from 4 Hz to 2.00 kHz, using either the internal frequency synthesizer or an external source as the reference. Chopping mode options are selectable at the fundamental, a harmonic (2 to 15), or even a sub-harmonic (1/2 to 1/15) of the reference.


* Jitter measured peak-to-peak (typical) with Sync set to Internal and Mode set to Normal.

Stability 100 ppm after one hour warm-up
Drift Less than 10 ppm/°C
Accuracy < 1/5 of least significant digit
Resolution 3 significant digits
Range limits (EXT) 4 Hz to 2.00 kHz
Input Type Sync InTTL-level pulse
Frequency Limit Same as internal oscillator
Pulse width ≥ 1 µs
Sync Out TTL level square wave
May be used as free-running oscillator
when using EXT+, EXT- or Vext Sync setting
Fouter TTL-level square wave at the chopping frequency
OUT 1 TTL level pulse: 
5*Fouter in NORMAL mode 
(H/S)*Fouter in H/S mode
OUT 2 TTL level pulse: 
[H/(7*S)]*Fsync in H/S mode
Range -180.0° to +179.0°
Resolution 0.1°, increasing to 0.25° at 2.0 kHz
Harmonic (H) 1 to 15
Subharmonic (S) 1 to 15
Voltage 0 to 10.0 VDC
Control Range 0 to 100% of maximum chopping frequency
Net Weight 2.59 kg [5.7 lbs], including chopper head
Electrical Ratings 100 to 240 VAC, 50 to 60 Hz
25 Watts
Operating Environment 10°C to 40°C [50°F to 104°F]
≤ 90% humidity, non-condensing
Storage Environment 0°C to 50°C [32°F to 122°F]
≤ 90% humidity, non-condensing
Altitude < 3000 meters [10000 feet]
Pollution Degree 2