Compact, high resolution, four wave lateral shearing interferometer

A simple, ultra-compact, four wave achromatic interferometric technique is used to measure with high accuracy and high transverse resolution wavefront of polychromatic lightsource. The wave front to be measured is replicated by a diffraction grating into four copies interfering together leading to an interference pattern very similar to the intensity distribution obtained in the focal plane of a Shack-Hartmann microlens array. The grating is made of optical glass modulated in depth on top of which a chromium mask is printed. The amplitude mask acts like a Hartmann plate. Used in association with the phase mask, it allows suppression of the unwanted zero and second orders. A CCD detector located in the vicinity of the grating records the interference pattern. This new wavefront sensor is able to resolve wavefront spatial frequencies 3 to 4 times higher than a conventional Shack-Hartmann technique using an equivalent CCD detector. Its dynamic is also much higher.