Mid-spatial frequency errors sit in the spatial frequency band between figure errors (measured by conventional interferometers) and surface roughness (measured by profilometers). They matter increasingly in high-performance optical systems — where MSF errors drive straylight, reduce contrast, and limit system throughput. The Ä9|9MP is ÄPRE’s purpose-built answer to this measurement challenge.
The 9MP camera-limited optical design, combined with controlled spatial and temporal coherence, delivers the spatial resolution needed to resolve MSF structure while maintaining the speed and ease of use expected from a production-grade interferometer. The system is available in bench-top form for lab and R&D use, or as a fully automated platform for integration into production workflows.
Like all ÄPRE systems, the Ä9|9MP runs REVEAL metrology software — with traceable data acquisition, fast report generation, and free lifetime upgrades.
Ä-Series | 9MP
| SYSTEM OVERVIEW |
| Measurement Capability |
Mid-Spatial Frequency Surface Structure |
| Output Diameter |
9mm |
| Working Distance/Fixed Focus |
Nominally 34.5mm (Fixed) |
| Interferometer Size (L x W x H) |
45.6 x 15.3 x 16.4cm |
| Weight |
4.5kg |
| Spatial Coherence Control |
Virtual Extended Source |
| Measurement Techniques |
Fast/Low-Noise Synchronous and Vibration-Tolerant PSI |
| Light Source |
SpectrÄ 2.0 |
| Alignment System |
Not Required with 9mm Field of View |
| Variable Coherence Length |
0.15 mm to 1.0mm |
| Output Polarisation |
Circular |
| Camera Resolution |
3000 x 3000 pixels |
| Camera Frame Rate (Max) |
≤ 75 Hz (source dependent) |
| Shutter Speed (Shortest) |
≥ 5 µs |
| Digitisation |
8 Bit |
| Mounting Configurations |
Horizontal or Vertical Manual, Semi-Automated or Automated |
| PERFORMANCE |
| Spatial Frequency Range |
0.2 l/mm to 160 l/mm |
| Fringe Resolution |
>1,000 fr/aperture |
| Retrace Error @ 512 Fringes |
<λ/15 |
| Noise Floor |
<30 pm RMS |
| Flat PSD Response |
0.1 l/mm to 160 l/mm |
| Standard Part Reflectivity |
0.5% to 40% Other Options Available |
| OPERATIONAL ENVIRONMENT |
| Temperature |
15°C to 30°C |
| ΔT/Δt |
<1°C per 15 min |
| Humidity |
5 to 80% Relative, Non-Condensing |
| Vibration Isolation |
Isolation System Required |
See Datasheet for full specifications.
Mid-Spatial Frequency Surface Characterisation
Measurement of MSF errors on precision optical surfaces — lenses, mirrors, flats — where conventional interferometers lack the spatial resolution to resolve sub-aperture polishing artefacts.
Advanced Polishing Process Control
Characterise and monitor MSF error evolution through the polishing process to guide corrections and verify final surface quality against specification.
High-Specification Imaging & Laser System Optics
Final inspection of optics for systems where MSF errors drive straylight, reduce Strehl ratio, or limit laser beam quality.
R&D Surface Metrology
