High LDT Coatings
Technical requirements:
1.Aperture:D1230
2.Coating:Reflecting dielectric coatings;wave band:420nm～800nm; average reflectivity:≥97%
3.Eccentricity between the primary mirror's optical axis and the excircle:≤0.5mm
4.Uncoated mirror surface:PVr≤λ/4;RMS ≤λ/40(λ=632.8nm)
5.Coated mirror surface:PVr ≤λ/3;RMS ≤λ/30(λ=632.8nm)
6.Error of radius of curvature at top:≤1mm
7.Perpendicularity between the optical axis and back face A:0.05mm
| Precision of Optical Machining | |
| Optical machining precision | ≤0.5mm |
| Size | φ266 |
| Error of radius of curvature at top | ≤1mm |
| Perpendicularity between the optical axis and end face A | 0.05mm |
| Roughness of reflecting surface | ≤2nm |
| Uncoated mirror surface flatness | PVr≤λ/4,RMS≤1/40 (λ=632.8nm) |
Result of the surface flatnes test inthe 0°direction in a φ1200mm aperture range before coating of the large-field primary miror.
Technical difficulties:
1.Coating requirements:Reflecting dielectric coatings;wave band:420nm～800nm;average reflectivity:≥97%(angle of incidence:<15°)(The thick coatings results in some difficulties.)
2.Due to the large product size,the coatings uniformity is difficult to control.
3.Coated surface accuracy:PVr ≤λ/3;RMS ≤λ/30(λ=632.8nm)
| Zone | Begin | End | Divisor | Area | Result |
| 1 | 420.00 | 800.00 | 380.000 | 37443.539 | 98.536 |
| 2 |