Sutech Optical
 
FAQ
What are magnetic resonant optical choppers?
Why can't a light source be simply turned on and off instead of using a chopper?
What is the lead time on Sutech Optical choppers
Can the Sutech Optical chopper vanes produce special light profiles?
What is duty cycle for a magnetic resonant optical chopper?
Can first surface mirrors be used as a chopper vane?
Can Sutech Optical choppers be used in a vacuum?
Can the chopper aperture size be adjusted during operation?
Can Sutech Optical choppers be operated close to halogen bulbs?
How much power is required for a Sutech Optical resonant chopper?
What are the limitations with resonant choppers?
Can multiple Sutech Optical choppers be phase locked to work together?
What is the package size of a Sutech Optical resonant chopper?
Can choppers operate with a single vane?
Why are Sutech Optical magnetic choppers used over conventional rotating choppers?
Does the magnetic chopper alter the spectral content of the passing light beam?
Can you get custom choppers from Sutech Optical?
Can you drive Sutech Optical choppers directly from a synthesized square wave?
Can you drive Sutech Optical magnetic choppers higher or lower than its resonant frequency?
What are typical applications with Sutech Optical magnetic resonant choppers?

Q: What are magnetic resonant optical choppers?
A: A resonant magnetic chopper is a precision tuning fork with small mechanical shutters affixed at the tips. As it vibrates, the shutters move towards each other during the first half of the cycle and moves away from each other in the second half of the cycle. The frequency is set by the natural resonance of the tuning fork. Drive is provided by an electromagnetic coil. When the shutters are closed, it blocks the light and when open, light passes freely.

Q: Why can't a light source be simply turned on and off instead of using a chopper?
A: In some applications at low frequency, the light source can be turned on and off. The limitation here is speed as governed by the thermal time constant of the filament. To achieve maximum signal to noise in many applications (especially at near infrared wavelengths), the light source must be modulated by a chopper to work at the best sensitivity point of the detector.
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Q: What is the lead time on Sutech Optical choppers?
A: Standard optical choppers with 570Hz and 800Hz have normal lead time of 3 weeks, but short orders can typically ship in less time. Please contact Sutech Optical on specific product models and special applications.

Q: Can the Sutech Optical chopper vanes produce special light profiles?
A: Yes. Sutech Optical can offer custom etched chopper vanes for special scanning application.
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Q: What is duty cycle for a magnetic resonant optical chopper?
A: The most popular duty cycle is 90% where light is block only 10% of the time. With this configuration, a beam diameter that fills the maximum aperture size will produce a sinosoid waveform with a 10% dark period at the baseline.

Q: Can first surface mirrors be used as a chopper vane?
A:
Yes. Sutech Optical offers first surface mirror vanes for multiplex application.
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Q: Can Sutech Optical choppers be used in a vacuum?
A: Yes. Sutech Optical chopper offers specially prepared choppers that functions in high vacuum. Contact Us for more information.

Q: Can the chopper aperture size be adjusted during operation?
A: Yes. Sutech Optical choppers operate at one fixed frequency, but the aperture size can be varied by changing the drive parameters. Higher drive signals will produce larger aperture sizes up to maximum specifications.
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Q: Can Sutech Optical choppers be operated close to halogen bulbs?
A: Yes. Sutech Optical choppers are built with alloys that can be in close proximity to a hot bulb source. Chopping of a halogen source is a typical application for UV-VIS spectrometers.

Q: How much power is required for a Sutech Optical resonant chopper?
A: 20mW typical, 100mW maximum.
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Q: What are the limitations with resonant choppers?
A: As chopping frequency increase, the aperture size decreases,. Beyond 1000Hz, the aperture size may be too small to use easily. When freqencies are very low, the chopper length is longer and the aperture size gets larger. However, it will become more sensitive to vibration and shock.

Q: Can multiple Sutech Optical choppers be phase locked to work together?
A: Yes. The phase difference between the master and one or more slave choppers can be varied and synchronized.
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Q: What is the package size of a Sutech Optical resonant chopper?
A: Typical package size is 2” x 0.7” x 0.6”. Integrated chopper package with built-in light source or detector occupies a small footprint of ~ 2.8 cubic inches (see section on technical drawings).

Q: Can choppers operate with a single vane?
A: Yes. Sutech Optical offers custom choppers where only one tine of the tuning fork is used and a dummy load is fixated to the other tine. Contact Us for more information.
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Q: Why are Sutech Optical magnetic choppers used over conventional rotating choppers?
A: The Sutech Optical magnetic resonant choppers have a much smaller form factor and footprint than rotary light choppers. It also requires very little power and offers very high reliability. It has no moving parts and can tolerate sudden shock and vibration without damage.

Q: Does the magnetic chopper alter the spectral content of the passing light beam?
A: No. The light passes through air when the shutters are open and does not alter the spectral content of the light beam.
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Q: Can you get custom choppers from Sutech Optical?
A: Yes. Sutech Optical can help in designing compact choppers and drive circuits for different optical instruments. Light sources and special detectors can also be integrated into a custom package.

Q: Can you drive Sutech Optical choppers directly from a synthesized square wave?
A: Yes. Sutech Optical offers the CF chopper models that are tuned very close to the specified operating frequency. (See the drive circuit section for additional details.)
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Q: Can you drive Sutech Optical magnetic choppers higher or lower than its resonant frequency?
A: No. Sutech Optical choppers have very high Q and cannot be forced by the drive circuit to operate outside its resonant frequency.

Q: What are typical applications with Sutech Optical magnetic resonant choppers?
A: The majority of applications involve spectrometers where increased signal to noise performance is required. Performance using chopped light can be 20X or more greater than unchopped approaches. (Refer to application section for detail examples.) Typical application categories include:
  1. spectrophotometers and grating spectrometers
  2. bolometers and radiometers
  3. open path detection systems
  4. laser telemetry systems
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Sutech Optical
7980 Kingsbury Drive
Hanover Park, Illinois 60133
P: (630) 855-5068 F: (630) 855-5068
sales@sutechoptical.com