产品指标如下：

Material                                       Zerodur glass or zero-expansion substitute

Dia tolerance (inch)                       +0, -0.005

Dia tolerance (mm)                        +0, -0.13

Center Thickness tolerance              ±0.010” (±0.25 mm)

Clear Aperture                                85% Central Diameter

Parallelism                                       3 arc min

Surface Accuracy                             1/4 wave at 633 nm

Surface Quality                                60/40

Coating                                          Protected Silver