Biconcave Lenses, φ20 mm, Focal Distance: -90 mm, Back Focus: -90.66 mm, Material : BK-7

[Features]
- Biconcave lenses have negative focal length and are used for image contraction and divergence.
[Specifications]
- Material: BK-7
- Outer diameter (φmm): 20
- Focus distance (mm): -90
- Bag focus (mm): -90.66
- Medium thickness (mm): 2
- Koba meat (mm): 3.05
- Design wavelength: 587.6 nm
- Refractive index: 1.51680/nd
- Chamfer (45°): 0.2-0.5 mm
- Tolerance range Outer diameter: φ+0/-0.1 mm
- Tolerance range Center thickness: ±0.2 mm
- Tolerance range Focal length: ±2%
- Tolerance range Surface quality: MIL60-40
- Tolerance range Eccentricity: within 3 minutes (3')