630-mm Large-aperture Phase-Shifting Interferometer

A large-aperture Phase-Shifting interferometer created for measuring the characteristics of optical elements with flat surfaces. The peculiarity of the interferometer is that as a result of the calibration of its reference plates an absolute measurements accuracy of ~λ/1000 (RMS) has been attained over the entire field of view.

A Large-aperture Phase-Shifting interferometer is constructed according to the Fizeau interferometer scheme (Fig.1). The field of view of the interferometer is 630 mm in diameter. The length of the interferometer is ~4.2 m. The interferometer is mounted on a table with pneumatic supports to reduce vibrations (Fig.2). Interferometer main feature is to achieve an absolute measurement accuracy of ~λ/1000 (RMS) over the entire field of view.

One of the key parts of the interferometer is its software. It is intended for recording the initial data on the intensities of interference patterns, their subsequent processing, and the presentation of experimental results in a form suitable for their use. Due to the interferogram phase shifting by tuning the probing-radiation wavelength, this interferometer is also capable of measuring the optical thickness and surface profiles of plane-parallel plates.

Interferometer Image
Absolute measurements accuracy
λ/1000 RMS (λ = 632.8 nm) on a 630-mm field of view
Two fields of view:
- 630 mm
- 100 mm
Processing of measurement results
Special software