Prism compensation based on prism ring

[billy_ntu]

Hi,

I need help to find formula to calculate the prism 'wedge angle', and how to do prism compensation based on different 'blank front curve' and 'prism ring diamete'r?

Meaning when we want to cut lens with certain prism value, if the prism ring diameter is changed, the machine have to be fitted with compensated prism (not the required one anymore).

Thanks

[JRS]

If you are blocking with the older methods, and then applying a prism ring around the outer block (or the very old wedges) - then the front of the lens shifts from block center.

The more the prism AND the steeper the front curve, the greater the deviation. Plus, if the lenses are not in either of the two traditional ring sets - you also may have an indexing issue. Rather software dependent at that end.

It is not a complex calculation and I'll dig it out and post it for you here when I get back to my desk (traveling).

[billy_ntu]

Hi Thanks, i will wait