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Doc 12536-D03 Rev D 9/19/2005
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Section 3: Description
The MC1000A Optical Chopper is a precision instrument utilizing advanced features to meet the most demanding applications.
The MC1000A uses a phased-lock loop (PLL) motor speed control design to precisely lock the chopping speed and phase to a
reference signal. An internal, crystal-stabilized frequency synthesizer provides an accurate and stable reference frequency for
ultra-low long-term frequency drift.
Unlike conventional, open-loop speed control designs, the PLL speed control circuit also allows the MC1000A chopper to be
synchronized to external reference signals, including other MC1000A choppers and reference sources such as DSP lock-in
amplifiers.
For more advanced measurements, the MC1000A can lock to a harmonic, sub-harmonic, or fractional-harmonic of an external
reference frequency. A second PLL circuit is used to multiply the external reference up to the 15
th
harmonic. This multiplier is
followed by a digital divider to divide the reference down to the 15
th
sub-harmonic. By combining both the frequency multiplication
and division together, a fractional harmonic can be obtained.
The MC1000A also supports 2-frequency chopping from a single chopper blade. A special blade is available with 7 outer slots
and 5 inner slots. This slot combination allows a single beam to be split and individually modulated for ratio metric experiments.
Other applications include pump-probe experiments where the pump beam is modulated at the outer frequency while modulating
a probe beam at the inner frequency. The MC1000A provides the sum and difference frequencies of the 2-frequency blade for
accurate lock-in detection of the frequency-mixed response.
A high quality, Swiss-made, rare earth magnet DC motor and a photo-etched chopper optical wheel drive the precision. The
compact optical head has a wide base for extra stability. The base is slotted for two ¼-20 mounting screws on 2” centers. The
interface cable uses standard RJ-45 modular connectors for easy setup.
The MC1000A controller includes a large, 4-digit, easy to read LED display for monitoring the chopper frequency. All of the
operating modes are accessible from streamlined, front panel push-button controls. Multiple user setups can be easily saved and
recalled from non-volatile memory. An RS-232 serial interface is included as a standard feature for remote interfacing the
MC1000A to other equipment.
Thorlabs offers a number of different blades to extend the range of the chopping frequency. A standard 10-slot blade is
included with the MC1000A. Two slot, 15 slot, 30 slot, 60 slot and the 2-frequency blades are also available.
Section 4: Parts List
Below is a list of all components shipped with the MC1000A Optical Chopper.
MC1000A Control Box
MC1000A Optical Chopping Head
MC1F10: 10-slot chopping blade
2 meter RJ-45 cable for optical head / control box interface
Operating Manual
US Power Supply Line Cord
125mA Fuse for use at 230VAC operation (250mA fuse installed in unit)
1/16” Allen Key for blade replacement
0.05” Allen Key for hub alignment.
(3X) 4-40 x 1/8” Phillips Pan Head Screws with Internal Tooth Washers
The following items are sold separately:
MC1F2: Two Slot Replacement Blade, 1 – 99Hz
MC1F15: 15-slot Replacement Blade, 38 – 1.5kHz
MC1F30: 30-slot Replacement Blade, 75 – 3kHz
MC1F60: 60-slot Replacement Blade, 150 – 6kHz
MC2F57: Dual Slot (5 Inner / 7 Outer) Replacement Blade
