Cylindrical Lens: Specs, Applications & Buying Guide
A cylindrical lens has curvature in only one direction instead of two, so it focuses light into a line instead of a point. That one-axis behavior makes it the standard tool anywhere an optical system needs to control a beam's shape in just one dimension.
Key Specifications at a Glance
| Parameter | Typical Value |
|---|---|
| Substrate | N-BK7, UV fused silica |
| Aperture | 5 mm–50 mm |
| Focal length range | 10 mm–500 mm |
| Surface accuracy | λ/4–λ/10 at 633 nm |
| Surface quality | 60-40 (standard), 20-10 (precision) |
| Coating | Uncoated / single-layer MgF2 / broadband AR |
How It's Different from a Spherical Lens
A spherical lens curves the same way in every direction, so it focuses light to a point. A cylindrical lens curves in only one axis and stays flat in the other, so it compresses or expands the beam along just that one axis, leaving the perpendicular axis untouched. Rotate the lens, and the direction of that line focus rotates with it.
Common Configurations
- Plano-convex cylindrical — converges light along one axis, the most common configuration
- Plano-concave cylindrical — diverges light along one axis
- Achromatic cylindrical doublet — corrects chromatic aberration for multi-wavelength systems, the same logic as a spherical achromat but along one axis only
Applications
- Reshaping an elliptical laser diode beam into a circular one
- Line-scan imaging and 3D metrology
- Anamorphic beam expansion
- Spectrometer and monochromator beam conditioning
Buying Tips
Because a cylindrical lens has no rotational symmetry, orientation matters as much as the lens itself — mark and mount it so its optical axis lines up correctly with your beam, since a rotated cylindrical lens shifts the whole line focus off-axis rather than just softening it. For beam-shaping work, also check the lens against your beam's f-number: standard plano-convex cylindrical lenses show noticeable spherical aberration at low f-numbers, and an acylindrical (aspheric cylindrical) surface may be worth the extra cost for high-NA laser applications.
