High Resolution with Low Spatial & Temporal Coherence
Ä9|9MP Fizeau interferometer enables practical Mid-Spatial Frequency measurement: Advanced camera limited optical design, controlled spatial and temporal coherence, and rapid data acquisition.
Low temporal and spatial coherence yields a sub-nanometer noise floor with 10's of picometer repeatability.
Temporal coherence control is accomplished using ÄPRE patented Spectrally Controlled Interferometry (SCI). In the short coherence mode interference fringes are isolated to the measurement surface. This eliminates interference fringes produced by other surface back reflections.
A spatial coherence buster minimizes speckles and spurious fringes, and other noise sources to minimize the measurement noise. Notably, the design achieves retrace error performance approaching 30 nm, even at maximum slopes of 1,200 fringes across the field of view
Advanced PSD Analysis and filtering reports the surface performance with easy to understand RMS result over a specified spatial frequency band.
- Spatial Frequency Range: 0.2 l/mm to 120 l/mm
- Fringe Solution: <1200 fr/aperture
- Retrace Error 3 @ 1200 fringes: < λ/15 4
- RMS Simple Repeatability 1: <0.03 nm RMS 2σ
- Accuracy 2: <0.15 nm RMS 2σ
- Measurable Part Reflectivity: 0.5% to 40% Other options available
1 RMS Simple Repeatability Test: The RMS variation of 30 sequential measurements with each measurement the average of 30 measurements
2 Accuracy Test: Acquire 30 sequential measurements. Average all measurements, subtract each measurement from the average. The mean plus 2 sigma of the subtracted measurements of these 30 is the accuracy
3 Retrace Error is defined as the PV residual error between a nulled measurement (the reference), subtracted from a measurement with 1200 fringes of tilt, and expressed by the first 36 Zernike polynomials
4 System resolution proven using commercially available LNL/NIST devloped BPRA resolution test artifact