摘要 : Most of biological and medical specimens are phase objects and cannot be observed directly under normal microscopes. Usually these specimens must be dyed, but it is harmful to living cells. Using the methods of phase contrast, sch... 展开 Most of biological and medical specimens are phase objects and cannot be observed directly under normal microscopes. Usually these specimens must be dyed, but it is harmful to living cells. Using the methods of phase contrast, schlieren, central dark ground etc., transparent objects can be changed into absorbed constructions 收起