Optical concave mirrors are precision reflective components designed for focusing, collecting, and imaging light without chromatic aberration. Plano concave mirrors are especially valued in optical systems where wavelength-independent performance, high reflectivity, and thermal stability are required.
Concave mirrors are widely used in laser beam manipulation, optical instrumentation, and high-quality imaging systems. Mirrors with longer focal lengths are particularly convenient for applications such as laser beam collimation, where controlled beam shaping and alignment are critical.
Working Principle of a Concave Mirror
A concave mirror features a reflective surface that curves inward, resembling a section of the inner surface of a sphere. When light rays parallel to the optical axis strike the mirror, they are reflected and converge at the focal point located in front of the mirror.
The distance between the mirror surface and this focal point is defined as the focal length. The image size and nature (real or virtual) depend on the object’s distance from the mirror and its position relative to the focal length, making concave mirrors highly versatile for both imaging and beam control.
Concave Mirror Specifications
| Parameter | Specification |
|---|---|
| Substrate | Optical glass, Fused Silica, H-K9L (N-BK7), Silicon, Germanium, Sapphire, Copper, Aluminum |
| Focal Length Tolerance | ±2% |
| Diameter Tolerance | +0 / −0.2 mm |
| Clear Aperture | > 90% of diameter |
| Thickness Tolerance | ±0.10 mm |
| Surface Quality | 60-40 scratch & dig |
| Surface Accuracy | λ/4 @ 632.8 nm |
| Coating | Metallic or dielectric high-reflection coating |
| Back Surface | Fine ground |
| Bevel | 0.2 – 0.3 mm × 45° |
Mirror Shapes Available
- Plano Mirrors
- Cylindrical Mirrors
- Prism Mirrors
- Spherical Mirrors
- Aspherical Mirrors
- Elliptical Mirrors
- Cone Mirrors
- Right-Angle Prism Mirrors
Reflection Coating Options
Protected Aluminum: Ravg > 90% (0.4–0.7 μm)
Enhanced Aluminum: Ravg > 92% (0.45–0.65 μm)
Protected Silver:
Ravg > 95% (0.5–0.8 μm)
Ravg > 95% (2–10 μm)
Protected Gold:
Ravg > 95% (0.8–2 μm)
Ravg > 84% (0.7–0.8 μm)
Dielectric Mirror Coatings: Ravg > 99.99% (>400 nm)
Applications of Concave Mirrors
- Shaving mirrors
- Head mirrors
- Ophthalmoscopes
- Astronomical telescopes
- Automotive headlights
- Solar furnaces
- Laser focusing and collimation systems