The numerical results show that the appearance of focal switch rests not only on the distance of aperture and lens but also on truncation parameter ; focal switch possibly occurs only when truncation parameter is between its critical maximum and minimum truncation parameters 數(shù)值結(jié)果表明:焦開(kāi)關(guān)的出現(xiàn)不僅與光闌透鏡分離量有關(guān),還與截?cái)鄥?shù)值密切相關(guān);僅當(dāng)截?cái)鄥?shù)取某一上、下限之間的值時(shí),才可能出現(xiàn)焦開(kāi)關(guān)。