planoconvex, with the convex side having spherical curvature.
ΚΠ
1757 T. BirchHist. Royal Soc. IV. 101 Mr Hooke shewed..a very expeditious way of finding all the possible foci of parallel rays refracted by a plano-spherical lens.
1997 Photo Trade News (Nexis) Mar. 24 The ports feature plano-spherical optical glass with O-rings seals.