Double-concave lens is normally used in combination with other lenses. Typical applications include laser beam expanders, optical character readers, viewers, and projection systems.
| ATTRIBUTE | SPECIFICATIONS |
| DIAMETER SIZE | smallest 3 mm |
| DIAMETER TOLERANCE | +0.1, -0.1mm |
| thickness tolerance | +0.1, -0.1mm |
| CENTRATION | 3 arc minutes |
| radius | +/-0.1% |
| CLEAR APERTURE | >90% |
| SURFACE FIGURE: POWER(N) | <3 fringes |
| SURFACE FIGURE: IRREGULARITY(N) | <0.5 fringe |
| SURFACE QUALITY | 40/20 scratch and dig |
| BEVEL | < 0.2 mm x 45° |
| COATING | With AR coating on outside surfaces |
