A concave mirror is a type of mirror with an inwardly curved reflective surface, whose cross-section is typically a segment of a parabola or a sphere. Its fundamental operating principle is the law of reflection. It can approximate the convergence of parallel rays close to its principal axis to a focal point, but exhibits spherical aberration, resulting in less perfect imaging compared to a parabolic mirror.
Stable structure, easy to install, and relatively low cost.
Exhibits spherical aberration: Marginal rays fail to converge perfectly to a single focus, degrading image clarity.
Completely free of chromatic aberration: As its principle relies on reflection rather than refraction.
| Material | H-K9L |
| Surface Flatness | λ/4@633nm |
| Backside Surface | Fine Ground (Not Polished) |
| Thickness Tolerance | ±0.2mm |
| Diameter Tolerance | +0.0,-0.1mm |
| Focal Length Tolerance | ±2% |
| Centration | ＜3 arc min |
| Surface Quality | 40/20-60/40 |
