Low stress or delayed calcium fluoride
Low stress and low delay are often positively correlated, with low stress representing a more uniform and homogeneous material, but with differences in crystal orientation, which can lead to differences in delay during multiple round trips or long distance transport. To obtain this material requires a consistent process of control of the raw material, crystal growth, crystal cutting and processing, crystal ultra-precision annealing, crystal grinding and polishing to remove as much internal thermal and external mechanical stress as possible, so that a maximum stress of 15 NM is involved.
15NM, 10NM, 6NM， 2NM
Product Advantage :
Maximum stress less than 6NM, maximum stress less than 2NM
Small sizes are mostly 2-3 types of material, large sizes all take 3-6 weeks
Low stress products are available on request for various requirements
Product Parameters :
Do wavefront distortions require low stress calcium fluoride?
The transmission wavefront is closely related to both the crystal quality and the polishing process. Lower material stresses can reduce processing difficulties and have a significant impact on the wavefront, but are not the only factor.
Can stresses be removed?
Stress relief is a relative concept; thermal stresses can often be released naturally through long periods of time, as well as gradually during subsequent cutting, grinding and polishing. The thermal stress is most fully released in the cutting of the crystals and, from a practical point of view, as long as the cutting does not crack, the subsequent grinding and polishing will basically not crack, but the mechanical and thermal stresses generated by rounding will not be eliminated in a short time, so that most lenses have a bad aperture at the edges and have a requirement to pass through the calibre.
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