4吋穿透式平面，1/20波長，長半徑量測

The 1/20 wave spec holds up exactly as promised—my long radius measurements are repeatable to the fraction of a fringe I needed. The 4" aperture sits rock-solid on the mount, and the transmission flat quality is clearly visible in the interferogram. Took me a bit to align the reference, but once it'

Set it up on my Zygo and it immediately delivered clean fringes on a 5-meter radius mirror. The 1/20 wave PV spec held true across the entire 4-inch aperture. Exactly the precision I needed for this job.

Interferometry on my long radius concave surfaces finally stopped being a guessing game once I switched to this flat. The 1/20 wave PV spec is genuine too, fringes stay straight right across the 4 inch aperture.