M-VIII · 1974
Meridian Interferometer
Splits a beam, recombines it, and reads the difference.
The Meridian divides a single wavefront across a 400 mm aperture and returns the two halves to the same detector. What comes back is a fringe pattern, and the spacing of those fringes is the measurement. Surface deviation resolves to one fortieth of a wavelength without contact.
Specifications
| Clear aperture | 400 mm |
|---|---|
| Wavefront error | λ/40 P-V |
| Source | 632.8 nm HeNe |
| Fringe stability | ±0.004 λ / hr |
| Thermal drift | 0.9 nm / K |
| Mass | 186 kg |
Applications
- 01Primary mirror figuring
- 02Optical flat certification
- 03Lens assembly verification