Strehl ratio and wavefront error

1. What is wavefront error?
2. How do you calculate wavefront error?
3. What is a good Strehl ratio?
4. How is Strehl ratio calculated?

What is wavefront error?

Wavefront error is defined as the difference between the reference wavefront phase, which is a constant phase or spherical phase, and the detected wavefront phase of one optical system. It is a very important criterion for the quality of the system, which can be used as merit functions for parametric optimization.

How do you calculate wavefront error?

The RMS wavefront error is given by a square root of the difference between the average of squared wavefront deviations minus the square of average wavefront deviation, or RMS= <(W-<W>)2>1/2 = (<W2>-<W>2)1/2, with the <...> brackets indicating an average value.

What is a good Strehl ratio?

When designing an optical system, the Strehl ratio is used to estimate the required correction of wavefront aberrations. The acceptable level of wavefront aberrations is different for every application but a value of 0.80 Strehl is conventionally used to define an optical system as “Diffraction limited” or ideal.

How is Strehl ratio calculated?

The Strehl ratio is a measure of the quality of optical image formation. The Strehl ratio equals the exponential of -4\[Pi] squared times the root mean square deviation of the wavefront squared divided by the wavelength squared.