On-axis & off-axis metrology

The characterization of the optical quality of a lens is a recurrent subject in the field of optics. The measurement of the wavefront is certainly the most complete way to assess the quality of an optical system. Imagine Optic has developed a whole range of instruments, based on wavefront measurement, perfectly adapted to the characterization of optical systems in single or double pass configuration.

In single pass configuration, the objective to be characterized is placed behind a collimator, and the wavefront measurement is performed with a wavefront analyzer from our HASO range placed behind the focal point of the objective. In double pass configuration, the use of the R-FLEX2 (self-illuminated wavefront sensor) allows easy measurement of the optical quality of the lens of interest. The R-FLEX2 illuminates this lens, via the focal plane, with a beam whose numerical aperture is adapted to that of the lens, and a plane mirror can be placed in autocollimation at the lens’s exit to measure its aberrations (see example of assembly below). Whether in single or double pass configuration, our measurement solutions allow on-axis and off-axis measurements.

Once the setup is done, a single wavefront measurement allows a complete characterization of the lens: both the measurement of aberrations decomposed on the basis of Zernike polynomials and the measurement of the MTF (Modulation Transfer Function) on all azimuths (what we call the 3D MTF). Knowing the aberrations is key for pinpointing the origin of possible problems in case the MTF of the lens is not as good as expected.

Application notes

Relevant products