Differential confocal radius of curvature measuring instrument is used for radius of curvature measurement.
Available model: 
1) measurement range: (-500, 1000)  mm, repeatiblity  0.001%;
2) measurement range: (-2000, 1000) mm, repeatiblity 0.0005%;
3) measurement range (-1000, 900) mm,  repeatibility 0.2 mm;
Bespoke design, please enquiry.