the refractive index(nd) of h-pk71 is 1.56907, and the dispersion coefficient(υd) is 71.30. the material is the glass with special dispersion. comparing to the other products in the same series, it has the relatively more negative dn/dt coefficient.
properties | h-fk61 | h-fk69 | h-fk76 | h-fk90 | h-fk95 | h-pk71 |
nd | 1.49700 | 1.59282 | 1.55032 | 1.45860 | 1.43700 | 1.56907 |
υd | 81.61 | 68.63 | 75.50 | 90.19 | 95.10 | 71.30 |
temperature coefficient of refractive index | -6.0 | -5.6 | -5.8 | -6.5 | -6.4 | -9.5 |
abnormal dispersion δpg,f | 0.0305 | 0.0145 | 0.0210 | 0.0450 | 0.0475 | 0.0199 |
thermal expansion coefficient α-50/80℃(×10-7/k) | 124 | 113 | 122 | 134 | 143 | 128 |
sag temperature ts (℃) | 489 | 608 | 576 | 467 | 433 | 509 |
density ρ (g/cm3) | 3.67 | 4.07 | 4.13 | 3.64 | 3.56 | 4.29 |