The VIRMOS Mask Manufacturing Unit

Mask Manufacturing Unit

The VIRMOS Mask Manufacturing Unit (MMU) is one of the main contributions of IFCTR to the VIRMOS project. Its purpose is

Further information

A collection of commented pictures is available describing the activities done until July 2000 for development and testing in Milan and the installation of the MMU in Paranal recently concluded.


Executive summary

A further page gives a block diagram of the MMU configuration and a summary of the MMU principles of operation.


Roughness of slit edge
at pixel size scale (0.12 mm)
Wq = 0.38 +/- 0.07 micron
where Wq is the rms of the filtered roughness profile above a 0.12 mm cutoff
Waviness of slit edge
(typical slit length 6-7 mm)
Wt = 1.3 +/- 0.3 micron
where Wt is the maximum peak-to-valley of the profile above a 2.5 mm cutoff
Slit width > 80 micron (limited by laser beam diameter 40 micron)
Slit length < 20 mm (shavings larger than this size cannot be disposed of by the exhauster
Positioning accuracy < 15 micron at the machine (allow for further 15 micron at the focal plane including thermal expansion of mask support)
Cutting speed 6 mm/sec for fine cutting (slits)
20 mm/sec for coarse cutting (contours)
Manufacturing time from 460 s for one "empty" mask (overhead due to Invar sheet mounting, connection set-up, cutting of contour and fixed features )
to 950 s for one mask with 200 slits