an·as·tig·mat /æˈnæstɪgˌmæt, ˌænəˈstɪg-/
  無象散透鏡
  an·astig·mat /æˈnæstɪgˌmæt, ˌænəˈstɪg-/ 名詞
  消像散透鏡,去像散透鏡
  anastigmat
       n : compound lens or lens system designed to be free of
           astigmatism and able to form approximately point images