 Equal radii
Having two inward curved sides and negative focal length
Used for image reduction and to spread light
Manufacturing Tolerances
Attribute |
Commercial standard |
Precision standard |
Material |
BK7 grade A, fine annealed |
BK7 grade A, fine annealed Fused Silica |
Diameter (Φ) |
+0/-0.5,+0/-0.25 |
+0/-0.20,+0/-0.15 |
Effective Focal Length (f') |
±5%,±2% |
±2%,±1% |
Irregularity of Fringes |
0.5 |
0.2 |
Surface Quality |
λ / 2,λ / 4 |
λ / 4,λ /10 |
Diameter (θ) Tolerance |
< +0.00/-0.20mm |
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Surface Flatness |
< λ / 4, < λ/10 @ 633 nm |
|
Cosmetics (Scratch-dig) |
80-50,60-40 |
20-10,10-5 |
Center Thickness (t) (mm) |
±5,±0.25 |
±0.15,±0.10 |
Centering Error (arc min) |
3 |
2,1 |
Clear Aperture |
85% of diameter |
90% of diameter |
Bevel (mm) |
Fine ground, beveled |
Fine ground, beveled |
Coating |
See attached coating chapter |
See attached coating chapter |
 All dimensions are in mm unless otherwise specified.
Different material, sizes, tolerance and coating are available upon request.
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