4D Technology Introduces AccuFiz® Duo Fizeau Interferometer

High precision, dynamic interferometer combines short and long coherence capabilities into one system for measuring an expanded range of optics.  

4D Technology, a subsidiary of Onto Innovation, announced today the launch of the AccuFiz Duo Fizeau interferometer.

The AccuFiz Duo dynamic interferometer uniquely combines the industry leading AccuFiz D short coherence capabilities with long coherence capabilities into a single system.

The AccuFiz Duo’s short coherence mode employs the same patented technology as the AccuFiz D, enabling vibration insensitive, on-axis, dynamic measurement for high accuracy measurement of optical grade surfaces. With a short coherence length source, the AccuFiz Duo measures flats and lenses without the need for coating surfaces to attenuate extraneous interference fringes. This mode enables surface error, transmitted wavefront error, remote cavity, wedge, optical thickness, and homogeneity measurements of plane parallel transparent surfaces down to 0.2mm thick.

The AccuFiz Duo’s additional long coherence source uses a stabilised HeNe laser and operates with all the benefits of a standard phase shifting Fizeau interferometer.  The long coherence mode enables very long cavity measurements and has spatial carrier dynamic mode as an option for vibration and turbulence mitigation.  It is also useful for standard radius of curvature measurements.  The 632.8nm HeNe source facilitates measurements with digital holograms as well.

The AccuFiz Duo Fizeau interferometer combines both short and long coherence sources into one system

“We are excited to introduce this new offering to the optics community. The AccuFiz Duo provides customers who are challenged with vibration and turbulence with a novel and modular dynamic system to enable them to measure a broader range of optics in a single system, saving on space and cost.”

Erik Novak, Vice President and General Manager of 4D Technology

The AccuFiz Duo has the same compact, lightweight design of the AccuFiz D, with 2 source modules to enable measurements on a broader range of optics in a lab or shop floor.

4D Technology’s user-friendly 4Sight Focus analysis software is common to both modes. 2D and 3D displays, filtering, and masking tools make it simple to quantify key surface shape; and Zernike, Seidel, geometric and diffraction analyses are all easy to perform.

The new AccuFiz Duo laser interferometer continues 4D Technology’s tradition of offering some of the world’s highest-performing interferometers, backed by industry-leading service and applications support.


The AccuFiz Duo, with its vibration insensitive short coherence mode and optional spatial carrier long coherence mode, can operate in environments where other instruments simply cannot. Use the AccuFiz Duo in the lab or right on the shop floor to measure:

  • Windows, thin glass, sapphire wafers
  • Domes and other curved, transparent components
  • Flats, spheres, prisms
  • Polished semiconductor components
  • Remote cavities
  • Solid cavities
  • Optical thickness and homogeneity
  • Transmission of components and systems
  • Rapid alignment of optical systems
  • Testing into vacuum and environmental chambers


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