Air-Gap Fabry-Perot Interferometer

CPI specializes in the construction of classic air-gap Fabry-Perot Interferometers (FPIs); our staff has over 40 years of collective FPI experience. These precision instruments yield maximum throughput for a given spectral resolution. Custom features include diameters from 1 cm to 6 inches and resonant cavity spacing from 3 μm to 6 cm.

  • Custom design and fabrication
  • Outer diameters from 1 cm to 6 inches
  • Resonant cavity spacing from 3 µm to 6 cm
  • Maximum throughput for a given spectral resolution
  • Operating ranges in the VIS, NIR, IR, MWIR, and LWIR
  • Optional pressure-pot
  • Optional temperature stabilization

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Liquid Crystal Fabry-Perot Interferometer

These are high-resolution (Doppler) filters and low resolution (imaging) filters. The technology uses nematic liquid crystal as the tuning medium in Fabry-Perot interferometers. Proprietary NUV - LWIR designs.

Please download and read a paper on the properties of CPI Liquid Crystal Tunable Filters.

For more information on Liquid Crystal Fabry-Perot Interferometers, click here.

  • Precise electronic wavelength selection
  • Completely solid-state design
  • Remarkable ease of use
  • Extreme resistance to shock and vibration
  • Rapid tuning on the order of milliseconds
  • Low-voltage analog input (0-10V max)
  • Excellent background rejection
  • Remarkable image quality
  • Diameters from 10 to 152 mm
  • Wavelength regions from 500 nm to 14 µm
  • Spectral resolution from 0.002 to 36 Å (VIS)
  • Absolutely no closed-loop control



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Lowell Doppler (Air-Gap) Interferometer

  • Telecentric optical system, with a 150mm objective lens
  • Andor iKon 1024 x 1024 scientific imaging camera
  • Two-mirror servo driven pointing system with stand-alone controller and web interface
  • ImageTool - data acquisition software
  • Remote laser calibration system
  • 19” rack mounted control systems and computer
  • Technical support for software, including remote login capability

Lowell Doppler (Air-Gap) Interferometer Profile *Click for larger view


Spatial Heterodyne Spectrometer

The Spatial Heterodyne Spectrometer (SHS) combines the high resolution and throughput of conventional interferometers with extreme robustness. The SHS does not require scanning to function at its full resolving power. The SHS can be made monolithic by fusing all of the main optical elements into a single block with no moving parts. CPI specializes in SHS with over 10 years of hands-on experience


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  • No mechanical, pressure, or voltage scanning required
  • Can be designed for any wavelength from 150 nm to 1.5 microns
  • Extremely robust
  • Spectral resolution as low as 0.001 nm in the visible
  • Size range continuous from < 5 mm to 100+ mm
  • Bandpass from a few nm to 100+ nm
  • Monolithic design available for increased robustness
  • Fourier transform spectrometer
  • Analysis software included