Patent ID: 7041612

Claim:
A lead-free and arsenic-free short flint glass with a refractive index 1.60≦n d ≦1.65, an Abbe number of 41≦ν d ≦52, a relative partial dispersion 0.551≦P gF ≦0.570 in the blue spectral region, a relative partial dispersion 0.507≦P Cs ≦0.525 in the red spectral region, a negative deviation of the relative partial dispersion from the normal line ΔP g,F ≦−0.0045 which has the following composition (in % by weight): SiO 2 >50–65 Al 2 O 3 0–7 B 2 O 3 0–6 Li 2 O 0–6 Na 2 O 3–11 K 2 O 0–6 MgO 0–12 CaO 1–12 BaO 0–8 La 2 O 3 0–15 Ta 2 O 5 0–10 Nb 2 O 5 4–20 ZrO 2 >10–20 Σ(CaO + MgO + BaO) 1–25 Σ(Na 2 O + K 2 O + Li 2 O) 3–20 SiO 2 /(ZrO 2 + La 2 O 3 + Nb 2 O 5 + Ta 2 O 5 ) 1.5–2.3.