When integrated in a reflection setup, the Phasics SID4 wavefront sensors can perform surface characterization. Kaleo software outputs the 3D surface map and the radius of curvature of convex or concave surfaces, such as lenses, mirrors, or molds. All surface quality parameters defined by the ISO 10110 standard such as surface irregularities, roughness, and waviness are calculated from this measurement. Surface profiles can also be extracted in any direction and results can be compared to the theoretical surface.
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Flat and slow surface measurement setup
In order to perform surface measurement, the beam is expanded to be adjusted to the size of the area of interest. The surface under test is imaged onto the SID4 wavefront sensor. First, a reference measurement is performed with a reference flat and the test sample is aligned and measured. The measured wavefront is twice the topography of the test surface.
Concave surface measurement setup
For concave surface measurement, a condenser is added to the optical setup in order to illuminate the surface under test with the right numerical aperture.
Convex surface measurement setup
The same approach with a condenser is used to qualify convex surfaces.
Measurement examples
Aspherical surface & shape error
Aspherical surface shape and error to design measured with QWSLI (SID4 wavefront sensor)
Flat glass surface topography
Surface topography measured with QWSLI (SID4-HR wavefront sensor)
Deformable mirror influence functions
Deformable mirror influences functions measurement performed with QWSLI (SID4 wavefront sensor)
Advantages
Complete and accurate
- Instantaneous complete 3D shape
- High dynamic range
- High-resolution map
Ease of use and versatility
- No CHG or null lens
- No stitching / scanning
- Non-contact measurement
Common-path interferometry
- No reference arm
- Insensitive to vibrations
- Easy alignment
