SLB-N Plano Concave Lenses - BK7
- Spherical plano concave lenses of BK7 are mostly used for monochromatic lights, such as laser beams or Fraunhofer lines.
- These lenses have negative focal lengths and are used when parallel beams are diverged.
- The lenses are polished carefully by selecting materials (striae, bubbles, inclusions, and homogeneity) and paying attention to dispersion (digs, scratches, and glosses) to prevent troubles with coherent light.
- Uncoated and coated with broadband multilayer AR coatings for visible are available.
- The focal length of a single lens is the distance from the principal point to the focal point. Our lenses are designed at the wavelength 546.1 nm (green mercury line [e]). Since focal lengths are wavelength dependent, they vary in the other wavelengths.
- The lenses coated with broadband multilayer antireflection coatings for visible have product numbers ending with an M.
Point
- Focal lengths of these lenses change as the shifts of refractive indexes of the material according to wavelength. (In the short wavelength range, the refractive index is higher and the focal length is shorter. In the long wavelength range, the refractive index is lower and the focal length is longer.) See the“Table of focal length shifts according to wavelength”on the page 157. Those data are applicable only for the lenses of Sigma Koki.
- If the concave surface is set to the parallel input beam side, the spherical aberration of the concave lens will be minimized.
Attention
- The edge thicknesses‘te’are theoretical values not including chamfer.
- Be sure to wear laser safety goggles when checking optical path and adjusting optical axis.
| Material | BK7 |
|---|---|
| Shape | Plano Concave |
| Design Wavelength(λc) | 546.1nm(n = 1.519) |
| Surface quality | 20 - 10 |
| Clear aperture | 90% of Actual Aperture (Uncoated) 85% of Actual Aperture(BMAR) |
| Coating | Uncoated Broadband Multilayer AR Coating for the Visible(BMAR) |
